{"slug":"meal-timing","name":"Meal timing and time-restricted eating","aliases":["Time-restricted eating","Eating window","Intermittent fasting (16:8)","Chrononutrition"],"kind":"lever","system":"chronobiology","unit":"hours (daily eating window)","unitNote":"The window is the span from the first calorie of the day to the last; trials assign it by clock time (8 a.m. to 4 p.m., noon to 8 p.m.) and two of the studies here define it as the interval holding 95 percent of a person's calories. Some studies measure the clock time of the last meal, or the midpoint between breakfast and dinner, instead of a window; those are quoted as the source states them.","answer":"Time-restricted eating lowers weight by about 1 to 2 kg in meta-analyses of short trials, mostly because people eat less: added to calorie restriction for a year it added nothing (139 adults), and an 8-hour window with no other guidance did nothing over 12 weeks (116 adults). The signal that timing itself matters is smaller and rests on early windows. In 8 men with prediabetes, a 6-hour window ending mid-afternoon lowered insulin and blood pressure with food intake matched and no weight loss, and in laboratory studies the same meal raises glucose about 17 percent more in the biological evening than in the morning.","summary":"Meal timing is the clock side of nutrition: when the first and last calories of the day fall, how long the window between them runs, and how much of the day's food lands in the evening. Clocks in the liver and gut are set by food rather than light, glucose handling is worse in the evening, and late eating raises hunger and lowers energy expenditure in controlled studies. The trials of shortened eating windows mostly show modest weight loss from eating less, with the strongest evidence for timing itself coming from early windows and small, short experiments. No guideline sets a window.","whatItIs":[{"text":"Time-restricted eating, in the definition used by its main investigators, means taking all of the day's calories within a consistent interval of less than 12 hours without overtly trying to eat less; the research paradigm uses a window of 8 to 12 hours. It grew out of two findings: that molecular clocks sit in almost every cell and anticipate recurring events such as the daily arrival of food, and that in animals a consistent daily feeding window keeps those clocks robust. In humans the question splits in two: whether a shorter window helps, and whether an earlier one does.","cites":["manoogian2022","chaix2019"],"grade":"C"},{"text":"The American Heart Association's 2017 scientific statement on meal timing and frequency notes that eating patterns have become harder to describe because skipping meals and snacking are more prevalent, reviews the cardiometabolic effects of breakfast skipping, intermittent fasting, the number of daily eating occasions and their timing, proposes research definitions for meals, snacks and eating occasions, and concludes that irregular eating patterns appear less favorable for a healthy cardiometabolic profile. It recommends intentional eating with mindful attention to the timing and frequency of eating occasions, and sets no number of hours.","cites":["stonge2017"],"grade":"A"},{"text":"What people actually do is wider than any trial window. When healthy adults who did not work shifts logged every ingestion event on a phone for three weeks, most ate frequently and erratically throughout their waking hours; fewer than 25 percent of calories were eaten before noon and more than 35 percent after 6 p.m.; the daily intake duration, defined as the interval holding 95 percent of events, exceeded 14 hours 45 minutes for half the group, and only 9.7 percent ate within 12 hours. Weekday-to-weekend shifts in eating time, which the authors called metabolic jetlag, were common. A 12-hour window is a reduction for most people, not a baseline.","cites":["gill2015"],"grade":"C"}],"origins":[{"text":"The body has more than one clock, and food sets the ones outside the brain. In 2000, restricting when mice could eat shifted the phase of circadian gene expression in peripheral tissues by up to 12 hours while the master clock in the suprachiasmatic nucleus, which follows light, did not move; the liver reset fastest, and after a week of daytime feeding every peripheral tissue examined had shifted together. In rats whose tissues glowed with each clock cycle, restricted feeding shifted the liver's rhythm by 10 hours within two days while the suprachiasmatic nucleus stayed locked to the light-dark cycle, which led the authors to suggest that peripheral clocks may be coupled to the brain's mainly through rhythmic behavior such as feeding. The same thing happens in people: when ten healthy young men had all three meals delayed by five hours in a laboratory, the rhythm of plasma glucose shifted by 5.69 hours and a clock gene in fat tissue by about an hour, while melatonin and cortisol, the markers of the central clock, did not move. Eating at the wrong hour is a way of telling the liver one time and the brain another.","cites":["damiola2000","stokkan2001","wehrens2017"],"grade":"C"},{"text":"The mouse work that launched the human trials made the point that when can matter as much as what. Mice given a high-fat diet for only 8 hours of each day ate the same calories as mice with round-the-clock access, yet were protected against obesity, high insulin, fatty liver and inflammation, with better-timed oscillations of the clock and its target genes. A follow-up in mice on several obesity-producing diets found the benefits proportional to the length of the daily fast, maintained when the schedule was interrupted by free access at weekends, and able to stabilize and reverse obesity and type 2 diabetes that were already established. Mice are nocturnal and the windows were set in their active phase, which is the main reason the findings had to be tested in people before they could be believed for them.","cites":["hatori2012","chaix2014","chaix2019"],"grade":"C"},{"text":"Human metabolism has a time of day, and it favors the morning. Studies that separate the internal clock from the sleep-wake and fasting-feeding cycle find that an identical meal produces about 17 percent more postprandial glucose in the biological evening (8 p.m.) than in the biological morning (8 a.m.), with 27 percent lower early-phase insulin from the beta cell, and that forcing the behavioral cycle 12 hours out of phase with the clock adds a further 6 percent to glucose through lower insulin sensitivity. Across ten acute studies pooled in a meta-analysis, the same meal eaten at night raised glucose more than in the day (standardized mean difference 1.66). A review of the human circadian literature finds rhythms in glucose, insulin, glucose tolerance, lipids, energy expenditure and appetite, several of which peak in the biological morning or around noon, and reads them as implying that earlier in the day is the better time to eat. These are the rhythms a late dinner runs against.","cites":["morris2015","leung2020","poggiogalle2018"],"grade":"B"},{"text":"Melatonin is one reason the evening is a poor time for carbohydrate. The hormone rises in the hours before habitual bedtime, and the beta cell carries receptors for it; a common variant in the melatonin receptor gene MTNR1B is a type 2 diabetes risk allele. In 21 healthy women, 5 mg of melatonin taken 15 minutes before a glucose load raised the glucose response by 186 percent in the morning and 54 percent in the evening, in the morning mainly by lowering insulin release and in the evening mainly by lowering insulin sensitivity. In 845 Spanish adults from a population that habitually eats late, each tested twice, a glucose load one hour before bedtime, when melatonin ran 3.5-fold higher than four hours before bedtime, produced 6.7 percent less insulin and 8.3 percent more glucose, and the impairment was stronger in carriers of the MTNR1B risk allele and traced to insulin secretion. The earlier crossover study from the same group found that a late dinner impaired glucose tolerance only in homozygous risk carriers. Cortisol belongs in the same picture: in the misalignment protocol its daily rhythm was completely reversed, and in a four-day early-window study the diurnal pattern of cortisol and the expression of several clock genes changed. On this shelf, meal timing sits upstream of fasting insulin, fasting glucose, HbA1c, triglycerides and cortisol, and alongside sleep, which shares its clock.","cites":["rubiosastre2014","garaulet2022","lopezminguez2018","scheer2009","jamshed2019"],"grade":"C"}],"labRange":{"typical":"No guideline sets an eating window. The American Heart Association's 2017 statement asks for intentional attention to the timing and frequency of eating and finds irregular patterns less favorable; the research definition of time-restricted eating is all calories within a consistent window of 8 to 12 hours (Chaix 2019; Manoogian 2022); the median adult in a 2015 survey ate across about 14 hours 45 minutes (Gill 2015)","claims":[{"text":"The American Heart Association's scientific statement is the nearest thing to a guideline, and it declines to prescribe a number. It finds that irregular eating patterns appear less favorable for achieving a healthy cardiometabolic profile and recommends intentional eating with mindful attention to the timing and frequency of eating occasions; the body of the statement reviews breakfast skipping, intermittent fasting, meal frequency and the timing of eating occasions as separate questions with separate evidence.","cites":["stonge2017"],"grade":"A"},{"text":"The 2019 consensus report on nutrition therapy for adults with diabetes and prediabetes, written for the American Diabetes Association, reviews intermittent fasting among the eating patterns, describes the early-window trial in men with prediabetes with its gains in insulin sensitivity, beta-cell responsiveness, blood pressure, oxidative stress and appetite, and states that the safety of intermittent fasting in people with special health situations, including pregnancy and disordered eating, has not been studied. It recommends no window.","cites":["evert2019"],"grade":"A"},{"text":"The research definition is a consistent daily window of less than 12 hours, commonly 8 to 12, with no deliberate attempt to cut calories; the trials below used 4, 6, 8 and 10 hours. The population median of about 15 hours is the reference point for what a reduction means, and the control condition in most trials was a window of 12 hours or more.","cites":["manoogian2022","chaix2019","gill2015"],"grade":"C"}]},"evidence":{"headline":"About 1 to 2 kg of weight loss across meta-analyses of short trials, from eating less; no added benefit over calorie restriction at one year (139 adults), and nothing from an 8-hour window alone over 12 weeks (116 adults). The circadian signal rests on early windows: insulin and blood pressure fell without weight loss in 8 men with prediabetes eating within 6 hours ending mid-afternoon, an early 8-hour window beat a midday one in 90 lean adults, and the same meal raises glucose about 17 percent more in the biological evening. No trial has measured events or deaths.","scale":{"min":4,"max":16,"ticks":[4,6,8,10,12,14,16]},"bands":[{"label":"Research definition of time-restricted eating: a consistent window of 8 to 12 hours","low":8,"high":12,"tone":"lab","source":"Chaix 2019; Manoogian 2022"},{"label":"4 to 6 hour windows: about 3 percent weight loss in 8 weeks, from eating about 550 kcal a day less","low":4,"high":6,"tone":"neutral","source":"Cienfuegos 2020"},{"label":"Early 6-hour window, dinner before 3 p.m.: lower insulin and blood pressure with no weight loss, 8 men","low":6,"high":6,"tone":"evidence","source":"Sutton 2018"},{"label":"8 to 10 hour windows: the trial range; weight loss when intake falls, more with an early window","low":8,"high":10,"tone":"evidence","source":"Liu 2022; Lin 2023; Jamshed 2022; Wilkinson 2020"},{"label":"12 hours or more: the control condition in most trials","low":12,"high":14,"tone":"neutral","source":"Jamshed 2022; Sutton 2018; Lin 2023"},{"label":"About 15 hours: the survey median; only about 10 percent of adults ate within 12","low":14,"high":16,"tone":"caution","source":"Gill 2015"}],"claims":[{"text":"The decisive trial for the weight question is the one-year study of 139 adults with obesity randomized to an 8-hour window (8 a.m. to 4 p.m.) plus calorie restriction or to the same calorie restriction alone, 1,500 to 1,800 kcal a day for men and 1,200 to 1,500 for women. At 12 months, with 118 (84.9 percent) completing, the time-restricted group had lost 8.0 kg and the calorie-restriction group 6.3 kg, a net difference of 1.8 kg that was not significant (95 percent confidence interval minus 4.0 to 0.4; P = 0.11); waist, body-mass index, body fat, lean mass, blood pressure and metabolic risk factors followed the same pattern, and adverse events did not differ. The authors' conclusion is that the window was not more beneficial than calorie restriction for weight, fat or metabolic risk.","cites":["liu2022"],"grade":"B"},{"text":"A window with nothing else attached did little. In the TREAT trial, 116 adults with overweight or obesity (mean age 46.5; 60 percent men) were randomized for 12 weeks to eat freely from noon to 8 p.m. and take no calories from 8 p.m. to noon, or to three structured meals a day. The time-restricted group lost 0.94 kg and the comparison group 0.68 kg, a between-group difference of 0.26 kg (minus 1.30 to 0.78; P = 0.63); in the 50 participants tested in person, there were no changes in fasting insulin, fasting glucose, HbA1c, energy intake or energy expenditure within or between groups, and the one significant between-group difference was a lower appendicular lean mass index in the time-restricted group (minus 0.16 kg/m2). The authors concluded that time-restricted eating, in the absence of other interventions, is not more effective for weight loss than eating through the day.","cites":["lowe2020"],"grade":"B"},{"text":"Against a true control, an 8-hour window does produce weight loss, and about as much as counting calories, because it cuts intake by about as much. In 90 adults with obesity (33 percent Black, 46 percent Hispanic) followed for 12 months, eating only between noon and 8 p.m. without counting lowered energy intake by 425 kcal a day and daily 25 percent calorie restriction by 405; weight fell 4.61 kg against control with the window and 5.42 kg with calorie restriction, a difference of 0.81 kg that was not significant. In 75 adults with type 2 diabetes and obesity (mean HbA1c 8.1 percent) followed for six months, the same noon-to-8 window lowered intake by 313 kcal a day and weight by 3.56 percent against control, while 25 percent calorie restriction lowered intake by 197 kcal and weight by a nonsignificant 1.78 percent; HbA1c fell 0.91 and 0.94 percentage points respectively, with no difference between them. Adherence tells the story: the window was kept on 6.1 days a week, and 68 percent of the calorie-counting group met their goal.","cites":["lin2023","pavlou2023"],"grade":"B"},{"text":"Shorter windows cut more and lose more, up to a point. In the first trial to compare them, adults with obesity randomized for 8 weeks to a 4-hour window (3 to 7 p.m.), a 6-hour window (1 to 7 p.m.) or no restriction lost about 3 percent of body weight on both windows against control, with comparable falls in insulin resistance and oxidative stress, and both groups ate about 550 kcal a day less without counting. The meta-analyses agree on the size of the effect: minus 0.90 kg across 19 studies with fat mass down 1.58 kg and fat-free mass preserved, systolic pressure down 3.07 mm Hg, fasting glucose down 2.96 mg/dL and triglycerides down 11.60 mg/dL; minus 1.60 kg across 17 randomized trials with 899 participants, with triglycerides, total and LDL cholesterol lower in participants with overweight and no effect on waist, body-mass index, HbA1c or blood pressure; and minus 1.07 kg across 11 studies, most of them of Ramadan fasting, with fasting glucose down 1.71 mg/dL. The weight effect is real, modest and explained by intake.","cites":["cienfuegos2020","moon2020","liul2022","pellegrini2020"],"grade":"A"},{"text":"The evidence that timing itself matters begins with one small, tightly controlled study. Eight men with prediabetes (mean age 56, body-mass index 32.2) ate every meal under supervision for five weeks on a 6-hour schedule with dinner before 3 p.m. and for five weeks on a 12-hour schedule, in random order, with food matched meal for meal and enough of it to hold weight; weight changed by 1.4 and 1.0 kg respectively, not significantly different. The early schedule did not change fasting or post-load glucose, but lowered fasting insulin by 3.4 mU/L and mean and peak insulin during a glucose tolerance test by 26 and 35 mU/L, improved insulin sensitivity and beta-cell responsiveness, lowered morning systolic and diastolic blood pressure by 11 and 10 mm Hg, and lowered the oxidative stress marker 8-isoprostane by 11 pg/mL, while fasting triglycerides rose 57 mg/dL, which the authors attribute to the longer fast before the morning test, 18 hours against 12. The one participant whose insulin worsened had a long history of overnight shift work.","cites":["sutton2018"],"grade":"C"},{"text":"Early beats late when the two are compared. In 90 adults with obesity (80 percent women, mean body-mass index 39.6) who all received weight-loss treatment with energy restriction, adding an 8-hour window from 7 a.m. to 3 p.m. for 14 weeks lost 2.3 kg more than eating over 12 or more hours (minus 3.7 to minus 0.9), an effect the authors equate to eating 214 kcal a day less, lowered diastolic pressure by 4 mm Hg and improved mood, without a significant extra loss of body fat in the full sample; the window was kept 6.0 days a week. In 90 healthy adults without obesity randomized for five weeks to an early 8-hour window between 6 a.m. and 3 p.m., a midday 8-hour window between 11 a.m. and 8 p.m., or no restriction, the early window lowered the insulin-resistance index HOMA-IR by 1.08 while the midday window did not change it (plus 0.39) and control did not (minus 0.05); the early group lost 1.6 kg against a 0.3 kg gain in controls, and only the early window improved fasting glucose, inflammation and gut microbial diversity. Energy intake fell 240 kcal a day on the early window and 159 on the midday one, so part of the early advantage may again be intake.","cites":["jamshed2022","xie2022"],"grade":"B"},{"text":"Shorter and matched experiments fill in the mechanism. In 15 men at risk of type 2 diabetes wearing glucose monitors, a 9-hour window for a week, whether 8 a.m. to 5 p.m. or noon to 9 p.m., lowered the glucose response to a test meal and fasting triglycerides, with no difference between the two placements except that only the early window lowered mean fasting glucose. In 16 healthy young men, two weeks of eating between 8 a.m. and 4 p.m. improved whole-body insulin sensitivity and muscle uptake of glucose and branched-chain amino acids against a group fed less to match the window group's 1.0 kg weight loss, so the gain was not the weight. In 11 adults with overweight, four days of eating from 8 a.m. to 2 p.m. instead of 8 a.m. to 8 p.m. lowered mean 24-hour glucose by 4 mg/dL and glycemic excursions by 12 mg/dL and shifted the diurnal pattern of cortisol and clock-gene expression; in the same design, 24-hour energy expenditure did not change (10 kcal a day), ghrelin fell 32 pg/mL and hunger ran more evenly. Where timed eating works, it works through appetite and insulin, not through burning more.","cites":["hutchison2019","jones2020","jamshed2019","ravussin2019"],"grade":"C"},{"text":"Ten-hour windows, the gentlest version, show the gap between a pilot and a trial. In 19 adults with metabolic syndrome whose baseline window averaged 15.13 hours, most of them taking a statin or blood-pressure medication, 12 weeks of a self-selected 10-hour window with no other advice lowered weight by 3.30 kg (3 percent), systolic pressure by 5.12 mm Hg and diastolic by 6.5, and LDL cholesterol from 104 to 92 mg/dL, with HbA1c falling significantly in the 12 who started with raised glucose or HbA1c; participants chose to begin between 8 and 10 a.m. and end between 6 and 8 p.m., and their timing became more regular. That study had no control group. When 100 Danish adults at high risk of type 2 diabetes (median age 59) were randomized to three months of a 10-hour window placed between 6 a.m. and 8 p.m. or to their habitual life, weight differed by 0.8 kg (minus 1.7 to 0.2), not significant; completers lost 1.0 kg more than controls, and nothing remained after three months of follow-up.","cites":["wilkinson2020","quist2024"],"grade":"B"},{"text":"Late eating has been tested with everything else held still. Sixteen adults with overweight or obesity lived through two laboratory protocols in random order, identical in food, activity, sleep and light, with meals in the second protocol delayed by 250 minutes. Late eating roughly doubled the probability of being hungry (from about 10 to about 20 percent), raised the ratio of ghrelin to leptin, lowered waking leptin by 16 percent, lowered energy expenditure during the waking day and 24-hour core body temperature, and shifted gene expression in fat tissue toward less fat breakdown and more fat storage. In the earlier misalignment study, 10 adults who ate and slept 12 hours out of phase with their clocks on a 28-hour day had 17 percent lower leptin, 6 percent higher glucose despite 22 percent higher insulin, a reversed cortisol rhythm, 3 percent higher mean arterial pressure and 20 percent lower sleep efficiency; 3 of the 8 with complete data showed post-meal glucose in the prediabetic range.","cites":["vujovic2022","scheer2009"],"grade":"B"},{"text":"The cohorts point the same way, with the usual limits. Among 420 adults on a 20-week weight-loss program in Spain, those who ate their main meal, lunch, after 3 p.m. lost less weight and lost it more slowly than earlier eaters, with no difference in energy intake, diet composition, estimated expenditure, appetite hormones or sleep; late eaters were more often evening types, ate lighter breakfasts and skipped breakfast more. In 3,362 adults from the same programs, those whose midpoint of intake fell after 2:54 p.m. had higher body-mass index, higher triglycerides and lower insulin sensitivity at baseline with no difference in intake or activity, and lost 80 g a week less. In 50,660 Adventist adults followed 7.42 years, people who ate one or two meals a day lost body-mass index relative to those eating three, snacking beyond three meals gained, an overnight fast of 18 hours or more went with falling body-mass index, and making breakfast the largest meal went with a yearly fall of 0.038 kg/m2 relative to making dinner the largest. In a 12-week trial of women with metabolic syndrome on about 1,400 kcal a day, a 700-kcal breakfast with a 200-kcal dinner beat the reverse for weight, waist, fasting glucose, insulin and HOMA-IR, and triglycerides fell 33.6 percent on the big breakfast and rose 14.6 percent on the big dinner.","cites":["garaulet2013","dashti2021","kahleova2017","jakubowicz2013"],"grade":"B"},{"text":"For hard outcomes there are only cohorts. In 103,389 French adults followed a median of 7.2 years, each hour later for the first meal of the day carried a 6 percent higher risk of cardiovascular disease (hazard ratio 1.06), each hour later for the last meal an 8 percent higher risk of cerebrovascular disease (1.08), a last meal after 9 p.m. against before 8 p.m. a 28 percent higher cerebrovascular risk (1.28), and each hour of nighttime fasting a 7 percent lower cerebrovascular risk (0.93), with the associations stronger in women. In 26,902 male US health professionals followed 16 years with 1,527 coronary events, men who skipped breakfast had 27 percent higher coronary risk (relative risk 1.27) and men who ate late at night 55 percent higher (1.55), associations mediated by body-mass index, hypertension, high cholesterol and diabetes. In 2,413 women with early breast cancer and a mean nightly fast of 12.5 hours, fasting less than 13 hours a night carried a 36 percent higher risk of recurrence (1.36) and nonsignificantly higher mortality, and each 2-hour longer fast went with lower HbA1c.","cites":["palomarcros2023","cahill2013","marinac2016"],"grade":"B"},{"text":"Breakfast skipping deserves its own honesty. Across six cohorts with 96,175 adults and 4,935 cases, ever skipping breakfast carried a 33 percent higher risk of type 2 diabetes (relative risk 1.33), falling to 22 percent after adjustment for body-mass index, and the risk plateaued at four to five skipped days a week (1.55). But when 13 randomized trials assigned people to eat or skip breakfast, those assigned to breakfast ate 259.79 kcal a day more and ended 0.44 kg heavier, in trials the authors rate as low quality and short; and across ten observational studies of large dinners, four found a link with body-mass index, five none and one the reverse, while five trials of smaller dinners pooled to a nonsignificant 0.89 kg. People who skip breakfast differ from people who do not, in sleep, chronotype, smoking and what they eat later, and no cohort can fully strip that out. The site treats the breakfast cohorts as a marker of a late-shifted day, not as proof that a morning meal protects.","cites":["ballon2019","sievert2019","fong2017"],"grade":"B"},{"text":"Shift work is meal timing imposed from outside. Across 12 observational studies with 226,652 participants and 14,595 cases, ever working shifts carried 9 percent higher odds of diabetes (odds ratio 1.09), stronger in men (1.37) and in rotating schedules, and the laboratory shows how: inverting the behavioral day raised post-meal glucose by 6 percent through lower insulin sensitivity, on top of the 17 percent evening penalty from the clock itself, and pooled acute studies find the night-time response to an identical meal larger than the daytime one. The glucose a shift worker eats at 2 a.m. is handled by a liver that has been told it is evening and a brain that has been told it is night.","cites":["gan2015","morris2015","leung2020"],"grade":"B"}]},"levers":[{"name":"An earlier window","effect":"the circadian benefit sits here, if anywhere: lower insulin, better glucose handling, slightly more weight loss","claim":{"text":"Every study that found a benefit of timing beyond calories used an early window. A 6-hour window ending before 3 p.m. lowered insulin and blood pressure with food matched in 8 men with prediabetes; an 8-hour window from 7 a.m. to 3 p.m. lost 2.3 kg more than a 12-hour-plus window in 90 adults with obesity all on energy restriction; an 8-hour window between 6 a.m. and 3 p.m. lowered HOMA-IR by 1.08 in lean adults while the same window placed between 11 a.m. and 8 p.m. did not; and two weeks of 8 a.m. to 4 p.m. improved muscle insulin sensitivity against matched weight loss. The one direct seven-day comparison found no difference between early and delayed 9-hour windows except that only the early one lowered fasting glucose. The early window is also the hardest to keep, because it ends where most social eating begins.","cites":["sutton2018","jamshed2022","xie2022","jones2020","hutchison2019"],"grade":"B"}},{"name":"A shorter window, from about 15 hours toward 10","effect":"cuts intake without counting; modest weight loss when it holds, none in the one randomized 10-hour trial","claim":{"text":"Eight overweight adults whose eating ran longer than 14 hours a day shortened it to a self-selected 10 to 11 hours for 16 weeks, with no instruction to eat differently, and lost 3.27 kg (95 percent confidence interval 0.91 to 5.62) with better sleep, less hunger at bedtime and more energy, maintained a year after they started. Nineteen adults with metabolic syndrome went from a 15-hour window to 10 for 12 weeks and lost 3.30 kg with lower blood pressure and LDL cholesterol. Both were uncontrolled; the randomized 10-hour trial in 100 adults at high risk of diabetes found a nonsignificant 0.8 kg difference at three months and nothing three months later. A shorter window works by removing the late calories, and only to the extent that it does.","cites":["gill2015","wilkinson2020","quist2024"],"grade":"B"}},{"name":"The same window every day, weekends included","effect":"keeps the peripheral clocks in step; the weekday-to-weekend shift is its own insult","claim":{"text":"The survey that found a median 14-hour-45-minute window also found weekday-to-weekend shifts in eating time common enough to be named metabolic jetlag, and its pilot participants were asked to hold the same window on both. In the human laboratory, a five-hour meal delay shifted the glucose rhythm by 5.69 hours without moving melatonin or cortisol, which is what a late Saturday dinner does to the liver's clock. The mouse data offer some forgiveness: protection held when the feeding window was interrupted by free access at weekends. Regularity is also what the sleep entry found predicted mortality in 60,977 adults; the two clocks are one system.","cites":["gill2015","wehrens2017","chaix2014"],"grade":"C"}},{"name":"The last meal: earlier and smaller","effect":"better evening glucose handling, most of all in carriers of the melatonin-receptor risk allele","claim":{"text":"A glucose load one hour before bedtime, against four hours before, produced 6.7 percent less insulin and 8.3 percent more glucose in 845 adults, with the impairment concentrated in MTNR1B risk-allele carriers and traced to insulin secretion; in the earlier crossover, a late dinner impaired glucose tolerance only in risk carriers. In the 103,389-adult French cohort, a last meal after 9 p.m. carried 28 percent higher cerebrovascular risk than one before 8 p.m. The size of the dinner is less settled than its hour: a 700-kcal breakfast with a 200-kcal dinner beat the reverse in one 12-week trial of women with metabolic syndrome, but five trials of smaller dinners pooled to a nonsignificant 0.89 kg. The entry recommends no clock time; it reports that the evidence for the hour is stronger than the evidence for the portion.","cites":["garaulet2022","lopezminguez2018","palomarcros2023","jakubowicz2013","fong2017"],"grade":"B"}},{"name":"Front-loading the day's calories","effect":"more weight loss on the same calories in one trial; a falling body-mass index in one cohort","claim":{"text":"On an isocaloric 1,400 kcal a day, women with metabolic syndrome who ate 700 kcal at breakfast and 200 at dinner lost more weight and waist than women on the reverse, with larger falls in fasting glucose, insulin and HOMA-IR and triglycerides down 33.6 percent against a 14.6 percent rise. Among 50,660 Adventists, those whose largest meal was breakfast lost 0.038 kg/m2 a year relative to those whose largest meal was dinner, and a large lunch gave a smaller but significant fall. Late lunch eaters in the Spanish program lost less weight on the same intake. The physiology above, with insulin sensitivity and beta-cell response highest in the morning, is the reason the pattern is plausible.","cites":["jakubowicz2013","kahleova2017","garaulet2013","poggiogalle2018"],"grade":"B"}},{"name":"Sleep and light, kept on the same clock as food","effect":"the central clock follows light; the liver follows food; misalignment between them is the harm","claim":{"text":"Late eating was harmful in the crossover study even with sleep, light and activity held identical, so it is not only a proxy for short sleep; and inverting the whole behavioral day against the internal clock raised glucose, reversed cortisol and cut sleep efficiency by 20 percent. Meal timing moved the glucose rhythm and the fat-tissue clock in men whose melatonin and cortisol rhythms stayed put, which is the definition of internal misalignment. The practical reading is that the first meal belongs after waking in daylight and the last well before the melatonin rise, and that a fixed wake time, morning light and a consistent eating window are one intervention, not three.","cites":["vujovic2022","scheer2009","wehrens2017"],"grade":"C"}},{"name":"Shift work: what the physiology allows","effect":"no trial has tested a timed-eating schedule in shift workers; the data say night calories cost more","claim":{"text":"Shift work carried 9 percent higher odds of diabetes across 226,652 people, the night-time glucose response to a meal is larger than the daytime one across pooled acute studies, and misalignment adds its own 6 percent on top of the 17 percent evening penalty. What follows from that is a hypothesis rather than a tested protocol: keep the carbohydrate-heavy meals in the hours the clock still reads as day, treat the night shift's food as the small end of the window, and hold the window as steady across the rotation as the roster allows. The one participant in the early-window trial whose insulin worsened had a history of overnight shift work, which the authors took as a reason to study altered clocks separately.","cites":["gan2015","leung2020","morris2015","sutton2018"],"grade":"D"}},{"name":"Glucose-lowering medication, adjusted before the fast","effect":"a lever that needs a prescriber; fasting doubled hypoglycemia on these drugs even with doses reduced","claim":{"text":"In 41 adults with type 2 diabetes on glucose-lowering medication who ate 500 to 600 kcal on two days a week for 12 weeks, fasting doubled the rate of hypoglycemia (rate ratio 2.05, 1.17 to 3.52) despite medication reduction, with no difference between consecutive and separated fast days; weight, HbA1c, fasting glucose and quality of life improved in both arms, and with education and dose reduction the number of events was lower than expected. The consensus report for the American Diabetes Association adds that the safety of intermittent fasting in pregnancy and disordered eating has not been studied. Anyone on insulin or a sulfonylurea who shortens their window has changed their dose requirement that day.","cites":["corley2018","evert2019"],"grade":"B"}}],"caveats":[{"text":"Most of what time-restricted eating does to weight is to make people eat less. The 4- and 6-hour windows cut intake by about 550 kcal a day; the noon-to-8 window cut it by 425 kcal a day against 405 for calorie counting and lost the same weight; added to calorie restriction for a year it added a nonsignificant 1.8 kg; and in the four-day calorimetry study an early window did not change 24-hour energy expenditure at all. Where a window helps a person, it is usually because it removed the evening calories they were not counting.","cites":["cienfuegos2020","lin2023","liu2022","ravussin2019"],"grade":"B"},{"text":"The independent circadian signal rests on small, short studies. The weight-matched evidence is 8 men for five weeks and 16 young men for two weeks; the early-versus-midday comparison is 82 completers for five weeks in lean adults; the four-day studies are 11 people each. The men's trial also fasted 18 hours before the early-window test and 12 before the control test, which the authors say may have understated the glycemic benefit but did raise fasting triglycerides by 57 mg/dL, and its insulin findings showed carry-over between arms. The direction is consistent and the physiology supports it; the size of the effect in free-living adults over years is unmeasured.","cites":["sutton2018","jones2020","xie2022","jamshed2019"],"grade":"C"},{"text":"Lean mass can go with the fat. The one between-group difference in the TREAT trial was a lower appendicular lean mass index in the time-restricted group (minus 0.16 kg/m2), the Ramadan-weighted meta-analysis found an inverse association with fat-free mass in its observational studies, and the 19-study meta-analysis found fat-free mass preserved. A shortened window compresses the hours in which protein can be eaten; the protein and resistance training entries describe what protects muscle during weight loss, and a window that makes those harder has a cost the scale will not show.","cites":["lowe2020","pellegrini2020","moon2020"],"grade":"B"},{"text":"Fasting windows are not for everyone, and the trials excluded the people most at risk. On glucose-lowering drugs, fasting doubled hypoglycemia despite dose reduction; the consensus report for the American Diabetes Association states that safety in pregnancy and disordered eating has not been studied; and in a national sample of 2,762 Canadian adolescents and young adults, 47.7 percent of women, 38.4 percent of men and 52.0 percent of transgender and gender-nonconforming participants reported intermittent fasting in the past year, and fasting was associated with eating-disorder psychopathology in every group, most consistently in women. Those are associations in young people, and they are the reason a fasting window is a question before it is an instruction.","cites":["corley2018","evert2019","ganson2022"],"grade":"C"},{"text":"The timing cohorts are confounded by who eats late. Late lunch eaters were more often evening types who skipped breakfast; the breakfast-skipping diabetes risk fell from 33 to 22 percent once body-mass index entered the model; the coronary associations with skipped breakfast and late-night eating were mediated by weight, blood pressure, cholesterol and diabetes; and the randomized breakfast trials ran the other way on weight. Late eating travels with short sleep, shift work, evening chronotype and a later, larger dinner, and a cohort measures the bundle.","cites":["garaulet2013","ballon2019","cahill2013","sievert2019"],"grade":"B"},{"text":"Studies do not agree on what a window is. Two define it as the interval holding 95 percent of a person's calorie-containing intake, which the metabolic-syndrome pilot notes runs longer than the first-to-last-calorie interval, under 11 hours on most of its participants' days against a 95 percent window of 15.13 hours; the trials assign clock times instead; and the cohorts use the hour of the last meal or the midpoint between breakfast and dinner. A number from one of these cannot be laid on another without saying which was measured.","cites":["wilkinson2020","gill2015","dashti2021"],"grade":"C"}],"seeAPhysician":["Any plan to shorten the eating window while taking insulin, a sulfonylurea or another medication that can lower blood sugar; the doses need adjusting before the first fasting day, not after a low.","Pregnancy, breastfeeding or trying to conceive; the safety of fasting windows in pregnancy has not been studied.","Any past eating disorder, or a present pattern in which food rules, skipped meals or the fasting hours have begun to feel compulsive.","An older adult who is underweight, frail or losing weight without trying, or anyone whose medications must be taken with food at set hours.","Lightheadedness, fainting, palpitations, shakiness or recurrent headaches during the fasting hours.","A shift worker, or anyone whose eating runs late by necessity, whose fasting glucose, HbA1c or triglycerides are rising; the schedule may be the cause and the fix needs to fit the roster.","Type 1 diabetes, or type 2 diabetes with any history of severe hypoglycemia, before any change in meal timing."],"openQuestions":["No trial of meal timing has measured heart attacks, strokes, cancers or deaths. Every endpoint is weight, a marker or a laboratory measurement over days to a year, and the outcome data are cohorts.","Whether an early window keeps its advantage over months and years in people with obesity is untested; the early-window trials run five weeks (8 men; 90 lean adults) to 14 weeks (90 adults with obesity), and the one seven-day comparison found no difference between early and delayed placements.","Whether the benefit is the window or the calories remains partly open. Only two studies matched intake and found a signal, both in men, and the early-window advantage in the 14-week trial was equivalent to 214 kcal a day.","Women are under-represented where the circadian signal is strongest: the weight-matched trials enrolled men only, the men-at-risk crossover was men only, while the cardiovascular cohort found its associations strongest in women. Whether sex, menopause or chronotype change the answer is unmapped.","Genotype as a moderator: the MTNR1B risk allele changed the effect of a late dinner on glucose tolerance in 845 adults, and no trial has assigned eating windows by genotype or chronotype.","Shift workers have no trial of a timed-eating schedule, and the one shift-work-history participant in the early-window trial got worse.","Whether time-restricted eating loses more lean mass than calorie restriction for the same weight loss is suggested by one trial's secondary outcome and not settled.","Durability: adherence in the trials ran about six days a week with weekly support, and the one trial with a follow-up phase lost its effect within three months of the intervention ending."],"questions":[{"q":"Does intermittent fasting work for weight loss?","a":"Modestly, and mostly because people eat less. Across meta-analyses of short trials, time-restricted eating lowers weight by about 1 to 2 kg against no restriction. When it is compared with ordinary calorie counting the difference disappears: an 8-hour window without counting lost 4.61 kg over a year against 5.42 kg for 25 percent calorie restriction, not significantly different, and adding an 8-hour window to a calorie-restricted diet for a year added a nonsignificant 1.8 kg. The one trial that assigned a noon-to-8 window with nothing else found 0.26 kg difference at 12 weeks. For some people a window is an easier rule to keep than a calorie count, and that is its real advantage."},{"q":"Is it better to eat early or late in the day?","a":"The evidence favors early, with honest limits. An identical meal raises glucose about 17 percent more in the biological evening than in the morning, melatonin rising before bed blunts insulin release, and a glucose load an hour before bedtime produced 8.3 percent more glucose than one four hours before in 845 adults. In trials, a 6-hour window ending before 3 p.m. lowered insulin and blood pressure with no weight loss in 8 men with prediabetes, an early 8-hour window beat a midday one for insulin resistance in 90 lean adults, and a 7 a.m. to 3 p.m. window lost 2.3 kg more than a 12-hour-plus window in 90 adults with obesity over 14 weeks. These are small and short; no trial has shown that moving dinner earlier prevents disease."},{"q":"Is skipping breakfast bad for you?","a":"The cohorts say people who skip breakfast have more diabetes and coronary disease, by about a third and a quarter respectively, but the associations shrink when weight is taken into account and the randomized trials point the other way: people assigned to eat breakfast ate about 260 kcal a day more and ended 0.44 kg heavier. Breakfast skipping travels with late nights, evening chronotype and a late, large dinner, and that bundle is what the cohorts measure. A skipped breakfast inside an early-ending day is a different thing from a skipped breakfast inside a day that ends at 11 p.m."},{"q":"How many hours should my eating window be?","a":"No guideline sets one. The research definition of time-restricted eating is a consistent window of 8 to 12 hours; the trials used 4, 6, 8 and 10; the control condition was usually 12 hours or more; and the median adult in a 2015 survey ate across about 14 hours 45 minutes, with only one in ten inside 12 hours. The 4- and 6-hour windows lost about 3 percent of weight in 8 weeks by cutting roughly 550 kcal a day; the randomized 10-hour trial lost nothing significant. The evidence supports moving the window earlier and keeping it consistent more than it supports any particular length."}],"citations":[{"id":"liu2022","authors":"Liu D, Huang Y, Huang C, et al.","title":"Calorie Restriction with or without Time-Restricted Eating in Weight Loss","journal":"New England Journal of Medicine","year":2022,"pmid":"35443107","doi":"10.1056/NEJMoa2114833","type":"rct","finding":"In 139 adults with obesity randomized for 12 months to an 8 a.m. to 4 p.m. window plus calorie restriction or calorie restriction alone, weight fell 8.0 and 6.3 kg respectively, a nonsignificant net difference of 1.8 kg (minus 4.0 to 0.4; P = 0.11); waist, body fat, lean mass, blood pressure and metabolic risk factors were consistent with the primary outcome.","url":"https://pubmed.ncbi.nlm.nih.gov/35443107/"},{"id":"lowe2020","authors":"Lowe DA, Wu N, Rohdin-Bibby L, et al.","title":"Effects of Time-Restricted Eating on Weight Loss and Other Metabolic Parameters in Women and Men With Overweight and Obesity: The TREAT Randomized Clinical Trial","journal":"JAMA Internal Medicine","year":2020,"pmid":"32986097","doi":"10.1001/jamainternmed.2020.4153","type":"rct","finding":"In 116 adults randomized for 12 weeks to eat freely from noon to 8 p.m. or to three structured meals, weight changed by 0.94 and 0.68 kg with a between-group difference of 0.26 kg (P = 0.63); in the 50 tested in person, no change in fasting insulin, glucose, HbA1c or energy intake, and a lower appendicular lean mass index in the time-restricted group (minus 0.16 kg/m2).","url":"https://pubmed.ncbi.nlm.nih.gov/32986097/"},{"id":"jamshed2022","authors":"Jamshed H, Steger FL, Bryan DR, et al.","title":"Effectiveness of Early Time-Restricted Eating for Weight Loss, Fat Loss, and Cardiometabolic Health in Adults With Obesity: A Randomized Clinical Trial","journal":"JAMA Internal Medicine","year":2022,"pmid":"35939311","doi":"10.1001/jamainternmed.2022.3050","type":"rct","finding":"In 90 adults with obesity (80 percent women) all receiving energy restriction, a 7 a.m. to 3 p.m. window for 14 weeks lost 2.3 kg more than a window of 12 or more hours (minus 3.7 to minus 0.9), equivalent to 214 kcal a day, lowered diastolic pressure 4 mm Hg and improved mood; body fat did not differ significantly in the full sample; adherence 6.0 days a week.","url":"https://pubmed.ncbi.nlm.nih.gov/35939311/"},{"id":"sutton2018","authors":"Sutton EF, Beyl R, Early KS, Cefalu WT, Ravussin E, Peterson CM","title":"Early Time-Restricted Feeding Improves Insulin Sensitivity, Blood Pressure, and Oxidative Stress Even without Weight Loss in Men with Prediabetes","journal":"Cell Metabolism","year":2018,"pmid":"29754952","doi":"10.1016/j.cmet.2018.04.010","type":"rct","finding":"In 8 men with prediabetes fed under supervision for five weeks each on a 6-hour window with dinner before 3 p.m. and a 12-hour window, with intake matched and weight stable, the early window lowered fasting insulin 3.4 mU/L, mean and peak post-load insulin 26 and 35 mU/L, systolic and diastolic pressure 11 and 10 mm Hg and 8-isoprostane 11 pg/mL, improved insulin sensitivity and beta-cell responsiveness, left glucose unchanged and raised fasting triglycerides 57 mg/dL.","url":"https://pubmed.ncbi.nlm.nih.gov/29754952/"},{"id":"wilkinson2020","authors":"Wilkinson MJ, Manoogian ENC, Zadourian A, et al.","title":"Ten-Hour Time-Restricted Eating Reduces Weight, Blood Pressure, and Atherogenic Lipids in Patients with Metabolic Syndrome","journal":"Cell Metabolism","year":2020,"pmid":"31813824","doi":"10.1016/j.cmet.2019.11.004","type":"rct","finding":"Single-arm study: 19 adults with metabolic syndrome, most on a statin or blood-pressure drug, with a baseline 95 percent eating window of 15.13 hours, kept a self-selected 10-hour window for 12 weeks and lost 3.30 kg (3 percent), with systolic pressure down 5.12 mm Hg, diastolic down 6.5 and LDL cholesterol from 104 to 92 mg/dL; HbA1c fell significantly in the 12 with raised baseline glucose or HbA1c.","url":"https://pubmed.ncbi.nlm.nih.gov/31813824/"},{"id":"cienfuegos2020","authors":"Cienfuegos S, Gabel K, Kalam F, et al.","title":"Effects of 4- and 6-h Time-Restricted Feeding on Weight and Cardiometabolic Health: A Randomized Controlled Trial in Adults with Obesity","journal":"Cell Metabolism","year":2020,"pmid":"32673591","doi":"10.1016/j.cmet.2020.06.018","type":"rct","finding":"Adults with obesity randomized for 8 weeks to a 4-hour (3 to 7 p.m.) or 6-hour (1 to 7 p.m.) window or no restriction lost about 3 percent of body weight on both windows, with lower insulin resistance and oxidative stress, and ate about 550 kcal a day less without counting.","url":"https://pubmed.ncbi.nlm.nih.gov/32673591/"},{"id":"xie2022","authors":"Xie Z, Sun Y, Ye Y, et al.","title":"Randomized controlled trial for time-restricted eating in healthy volunteers without obesity","journal":"Nature Communications","year":2022,"pmid":"35194047","doi":"10.1038/s41467-022-28662-5","type":"rct","finding":"In 90 healthy adults without obesity randomized for five weeks to an 8-hour window between 6 a.m. and 3 p.m., an 8-hour window between 11 a.m. and 8 p.m., or control (82 analyzed), the early window lowered HOMA-IR by 1.08 against plus 0.39 midday and minus 0.05 control, lost 1.6 kg against a 0.3 kg gain in controls, and alone improved fasting glucose, inflammation and gut microbial diversity; intake fell 240 and 159 kcal a day on the two windows.","url":"https://pubmed.ncbi.nlm.nih.gov/35194047/"},{"id":"pavlou2023","authors":"Pavlou V, Cienfuegos S, Lin S, et al.","title":"Effect of Time-Restricted Eating on Weight Loss in Adults With Type 2 Diabetes: A Randomized Clinical Trial","journal":"JAMA Network Open","year":2023,"pmid":"37889487","doi":"10.1001/jamanetworkopen.2023.39337","type":"rct","finding":"In 75 adults with type 2 diabetes and obesity randomized for six months to a noon-to-8 p.m. window without counting, 25 percent calorie restriction, or control, weight fell 3.56 percent with the window and a nonsignificant 1.78 percent with calorie restriction against control; HbA1c fell 0.91 and 0.94 points with no difference between them; intake fell 313 and 197 kcal a day; window kept 6.1 days a week.","url":"https://pubmed.ncbi.nlm.nih.gov/37889487/"},{"id":"lin2023","authors":"Lin S, Cienfuegos S, Ezpeleta M, et al.","title":"Time-Restricted Eating Without Calorie Counting for Weight Loss in a Racially Diverse Population: A Randomized Controlled Trial","journal":"Annals of Internal Medicine","year":2023,"pmid":"37364268","doi":"10.7326/M23-0052","type":"rct","finding":"In 90 adults with obesity randomized for 12 months to a noon-to-8 p.m. window without counting, 25 percent calorie restriction, or a control eating over 10 or more hours, intake fell 425 and 405 kcal a day and weight fell 4.61 and 5.42 kg against control, a nonsignificant 0.81 kg difference between the window and calorie restriction.","url":"https://pubmed.ncbi.nlm.nih.gov/37364268/"},{"id":"quist2024","authors":"Quist JS, Pedersen HE, Jensen MM, et al.","title":"Effects of 3 months of 10-h per-day time-restricted eating and 3 months of follow-up on bodyweight and cardiometabolic health in Danish individuals at high risk of type 2 diabetes: the RESET single-centre, parallel, superiority, open-label, randomised controlled trial","journal":"Lancet Healthy Longevity","year":2024,"pmid":"38588687","doi":"10.1016/S2666-7568(24)00028-X","type":"rct","finding":"In 100 adults at high risk of type 2 diabetes (median age 59) randomized to three months of a self-selected 10-hour window between 6 a.m. and 8 p.m. or habitual living, weight differed by a nonsignificant 0.8 kg (minus 1.7 to 0.2); completers lost 1.0 kg more than controls; no difference remained after three months of follow-up.","url":"https://pubmed.ncbi.nlm.nih.gov/38588687/"},{"id":"hutchison2019","authors":"Hutchison AT, Regmi P, Manoogian ENC, et al.","title":"Time-Restricted Feeding Improves Glucose Tolerance in Men at Risk for Type 2 Diabetes: A Randomized Crossover Trial","journal":"Obesity","year":2019,"pmid":"31002478","doi":"10.1002/oby.22449","type":"rct","finding":"In 15 men at risk of type 2 diabetes, 7 days of a 9-hour window, early (8 a.m. to 5 p.m.) or delayed (noon to 9 p.m.), lowered the glucose response to a test meal and fasting triglycerides with no difference by placement; only the early window lowered mean fasting glucose on continuous monitoring; insulin did not change.","url":"https://pubmed.ncbi.nlm.nih.gov/31002478/"},{"id":"jones2020","authors":"Jones R, Pabla P, Mallinson J, et al.","title":"Two weeks of early time-restricted feeding (eTRF) improves skeletal muscle insulin and anabolic sensitivity in healthy men","journal":"American Journal of Clinical Nutrition","year":2020,"pmid":"32729615","doi":"10.1093/ajcn/nqaa192","type":"rct","finding":"In 16 healthy young men, two weeks of eating between 8 a.m. and 4 p.m. improved whole-body insulin sensitivity and skeletal muscle uptake of glucose and branched-chain amino acids compared with a group fed less to match the 1.0 kg weight loss, so the benefit was independent of weight.","url":"https://pubmed.ncbi.nlm.nih.gov/32729615/"},{"id":"jamshed2019","authors":"Jamshed H, Beyl RA, Della Manna DL, Yang ES, Ravussin E, Peterson CM","title":"Early Time-Restricted Feeding Improves 24-Hour Glucose Levels and Affects Markers of the Circadian Clock, Aging, and Autophagy in Humans","journal":"Nutrients","year":2019,"pmid":"31151228","doi":"10.3390/nu11061234","type":"rct","finding":"In 11 adults with overweight in a 4-day crossover, eating from 8 a.m. to 2 p.m. instead of 8 a.m. to 8 p.m. lowered mean 24-hour glucose by 4 mg/dL and glycemic excursions by 12 mg/dL and altered the diurnal pattern of cortisol and the expression of several clock genes.","url":"https://pubmed.ncbi.nlm.nih.gov/31151228/"},{"id":"ravussin2019","authors":"Ravussin E, Beyl RA, Poggiogalle E, Hsia DS, Peterson CM","title":"Early Time-Restricted Feeding Reduces Appetite and Increases Fat Oxidation But Does Not Affect Energy Expenditure in Humans","journal":"Obesity","year":2019,"pmid":"31339000","doi":"10.1002/oby.22518","type":"rct","finding":"In 11 adults with overweight who ate from 8 a.m. to 2 p.m. and from 8 a.m. to 8 p.m. for 4 days each with intake and meal frequency matched, 24-hour energy expenditure did not differ (10 kcal a day), while ghrelin fell 32 pg/mL, hunger ran more evenly and fat oxidation rose.","url":"https://pubmed.ncbi.nlm.nih.gov/31339000/"},{"id":"jakubowicz2013","authors":"Jakubowicz D, Barnea M, Wainstein J, Froy O","title":"High caloric intake at breakfast vs. dinner differentially influences weight loss of overweight and obese women","journal":"Obesity","year":2013,"pmid":"23512957","doi":"10.1002/oby.20460","type":"rct","finding":"Women with overweight or obesity and metabolic syndrome randomized for 12 weeks to about 1,400 kcal a day as 700 at breakfast and 200 at dinner, or the reverse, lost more weight and waist on the big breakfast with greater falls in fasting glucose, insulin and HOMA-IR; triglycerides fell 33.6 percent on the big breakfast and rose 14.6 percent on the big dinner.","url":"https://pubmed.ncbi.nlm.nih.gov/23512957/"},{"id":"vujovic2022","authors":"Vujović N, Piron MJ, Qian J, et al.","title":"Late isocaloric eating increases hunger, decreases energy expenditure, and modifies metabolic pathways in adults with overweight and obesity","journal":"Cell Metabolism","year":2022,"pmid":"36198293","doi":"10.1016/j.cmet.2022.09.007","type":"rct","finding":"In 16 adults with overweight or obesity in a randomized crossover with nutrients, activity, sleep and light controlled, delaying meals by 250 minutes raised the probability of hunger from about 10 to about 20 percent, raised the ghrelin-to-leptin ratio, lowered waking leptin 16 percent, lowered waking energy expenditure and 24-hour core temperature, and shifted adipose gene expression toward less lipolysis and more adipogenesis.","url":"https://pubmed.ncbi.nlm.nih.gov/36198293/"},{"id":"scheer2009","authors":"Scheer FA, Hilton MF, Mantzoros CS, Shea SA","title":"Adverse metabolic and cardiovascular consequences of circadian misalignment","journal":"Proceedings of the National Academy of Sciences of the United States of America","year":2009,"pmid":"19255424","doi":"10.1073/pnas.0808180106","type":"laboratory","finding":"In 10 adults living 28-hour days for 10 days, eating and sleeping 12 hours out of phase with the internal clock lowered leptin 17 percent, raised glucose 6 percent despite 22 percent higher insulin, completely reversed the cortisol rhythm, raised mean arterial pressure 3 percent and lowered sleep efficiency 20 percent; 3 of 8 showed postprandial glucose in the prediabetic range.","url":"https://pubmed.ncbi.nlm.nih.gov/19255424/"},{"id":"morris2015","authors":"Morris CJ, Yang JN, Garcia JI, et al.","title":"Endogenous circadian system and circadian misalignment impact glucose tolerance via separate mechanisms in humans","journal":"Proceedings of the National Academy of Sciences of the United States of America","year":2015,"pmid":"25870289","doi":"10.1073/pnas.1418955112","type":"laboratory","finding":"In two 8-day laboratory protocols in healthy adults, postprandial glucose was 17 percent higher in the biological evening than the biological morning independent of the behavioral cycle, with 27 percent lower early-phase insulin, and circadian misalignment itself raised postprandial glucose a further 6 percent through lower insulin sensitivity.","url":"https://pubmed.ncbi.nlm.nih.gov/25870289/"},{"id":"wehrens2017","authors":"Wehrens SMT, Christou S, Isherwood C, et al.","title":"Meal Timing Regulates the Human Circadian System","journal":"Current Biology","year":2017,"pmid":"28578930","doi":"10.1016/j.cub.2017.04.059","type":"laboratory","finding":"In 10 healthy young men over 13 laboratory days, delaying all three meals by 5 hours shifted the plasma glucose rhythm by 5.69 hours and adipose PER2 rhythms by 0.97 hours while melatonin, cortisol, triglyceride and blood clock-gene rhythms did not move; meal timing synchronizes peripheral clocks in humans.","url":"https://pubmed.ncbi.nlm.nih.gov/28578930/"},{"id":"rubiosastre2014","authors":"Rubio-Sastre P, Scheer FA, Gómez-Abellán P, Madrid JA, Garaulet M","title":"Acute melatonin administration in humans impairs glucose tolerance in both the morning and evening","journal":"Sleep","year":2014,"pmid":"25197811","doi":"10.5665/sleep.4088","type":"rct","finding":"In 21 healthy women, 5 mg melatonin 15 minutes before a 75 g glucose load raised the incremental glucose area by 186 percent in the morning and 54 percent in the evening against placebo, in the morning mainly by lowering insulin release and in the evening mainly by lowering insulin sensitivity.","url":"https://pubmed.ncbi.nlm.nih.gov/25197811/"},{"id":"lopezminguez2018","authors":"Lopez-Minguez J, Saxena R, Bandín C, Scheer FA, Garaulet M","title":"Late dinner impairs glucose tolerance in MTNR1B risk allele carriers: A randomized, cross-over study","journal":"Clinical Nutrition","year":2018,"pmid":"28455106","doi":"10.1016/j.clnu.2017.04.003","type":"rct","finding":"In a randomized crossover, eating dinner when endogenous melatonin was elevated impaired glucose tolerance, more strongly in homozygous MTNR1B risk-allele carriers, and significantly only in them.","url":"https://pubmed.ncbi.nlm.nih.gov/28455106/"},{"id":"garaulet2022","authors":"Garaulet M, Lopez-Minguez J, Dashti HS, et al.","title":"Interplay of Dinner Timing and MTNR1B Type 2 Diabetes Risk Variant on Glucose Tolerance and Insulin Secretion: A Randomized Crossover Trial","journal":"Diabetes Care","year":2022,"pmid":"35015083","doi":"10.2337/dc21-1314","type":"rct","finding":"In 845 Spanish adults each given a 75 g glucose load 4 hours and 1 hour before habitual bedtime, melatonin was 3.5-fold higher in the late condition, which produced 6.7 percent less insulin and 8.3 percent more glucose; the impairment was stronger in MTNR1B G-allele carriers and attributable to reduced beta-cell function.","url":"https://pubmed.ncbi.nlm.nih.gov/35015083/"},{"id":"garaulet2013","authors":"Garaulet M, Gómez-Abellán P, Alburquerque-Béjar JJ, Lee YC, Ordovás JM, Scheer FA","title":"Timing of food intake predicts weight loss effectiveness","journal":"International Journal of Obesity","year":2013,"pmid":"23357955","doi":"10.1038/ijo.2012.229","type":"cohort","finding":"Among 420 adults on a 20-week weight-loss program, those who ate lunch, the main meal, after 3 p.m. lost less weight and more slowly than earlier eaters (P = 0.002), with similar energy intake, composition, estimated expenditure, appetite hormones and sleep; late eaters were more often evening types and skipped breakfast more.","url":"https://pubmed.ncbi.nlm.nih.gov/23357955/"},{"id":"dashti2021","authors":"Dashti HS, Gómez-Abellán P, Qian J, et al.","title":"Late eating is associated with cardiometabolic risk traits, obesogenic behaviors, and impaired weight loss","journal":"American Journal of Clinical Nutrition","year":2021,"pmid":"33022698","doi":"10.1093/ajcn/nqaa264","type":"cohort","finding":"Among 3,362 adults in a Spanish weight-loss program, those whose midpoint of intake fell after 2:54 p.m. had higher body-mass index, higher triglycerides and lower insulin sensitivity at baseline with no difference in intake or activity, lost 80 g a week less (505 against 585 g), and had higher odds of weight-loss barriers (1.22).","url":"https://pubmed.ncbi.nlm.nih.gov/33022698/"},{"id":"kahleova2017","authors":"Kahleova H, Lloren JI, Mashchak A, Hill M, Fraser GE","title":"Meal Frequency and Timing Are Associated with Changes in Body Mass Index in Adventist Health Study 2","journal":"Journal of Nutrition","year":2017,"pmid":"28701389","doi":"10.3945/jn.116.244749","type":"cohort","finding":"In 50,660 Adventist adults followed 7.42 years, one or two meals a day went with a falling body-mass index relative to three (minus 0.035 and minus 0.029 kg/m2 a year), more than three meals with a rise, an overnight fast of 18 hours or more with a fall, breakfast eating with a fall (minus 0.029), and breakfast as the largest meal with a fall of 0.038 relative to dinner as the largest.","url":"https://pubmed.ncbi.nlm.nih.gov/28701389/"},{"id":"palomarcros2023","authors":"Palomar-Cros A, Andreeva VA, Fezeu LK, et al.","title":"Dietary circadian rhythms and cardiovascular disease risk in the prospective NutriNet-Santé cohort","journal":"Nature Communications","year":2023,"pmid":"38097547","doi":"10.1038/s41467-023-43444-3","type":"cohort","finding":"In 103,389 adults followed a median 7.2 years, each hour later for the first meal carried a hazard ratio of 1.06 for cardiovascular disease, each hour later for the last meal 1.08 for cerebrovascular disease, a last meal after 9 p.m. against before 8 p.m. 1.28, and each hour of nighttime fasting 0.93 for cerebrovascular disease; associations were stronger in women.","url":"https://pubmed.ncbi.nlm.nih.gov/38097547/"},{"id":"cahill2013","authors":"Cahill LE, Chiuve SE, Mekary RA, et al.","title":"Prospective study of breakfast eating and incident coronary heart disease in a cohort of male US health professionals","journal":"Circulation","year":2013,"pmid":"23877060","doi":"10.1161/CIRCULATIONAHA.113.001474","type":"cohort","finding":"In 26,902 men aged 45 to 82 followed 16 years with 1,527 coronary events, skipping breakfast carried a relative risk of 1.27 and eating late at night 1.55, associations mediated by body-mass index, hypertension, hypercholesterolemia and diabetes; eating frequency was not associated.","url":"https://pubmed.ncbi.nlm.nih.gov/23877060/"},{"id":"marinac2016","authors":"Marinac CR, Nelson SH, Breen CI, et al.","title":"Prolonged Nightly Fasting and Breast Cancer Prognosis","journal":"JAMA Oncology","year":2016,"pmid":"27032109","doi":"10.1001/jamaoncol.2016.0164","type":"cohort","finding":"In 2,413 women with early-stage breast cancer and a mean nightly fast of 12.5 hours, fasting less than 13 hours a night carried a hazard ratio of 1.36 for recurrence and nonsignificant 1.21 and 1.22 for breast cancer and all-cause mortality; each 2-hour longer fast went with lower HbA1c (beta minus 0.37) and longer sleep.","url":"https://pubmed.ncbi.nlm.nih.gov/27032109/"},{"id":"ballon2019","authors":"Ballon A, Neuenschwander M, Schlesinger S","title":"Breakfast Skipping Is Associated with Increased Risk of Type 2 Diabetes among Adults: A Systematic Review and Meta-Analysis of Prospective Cohort Studies","journal":"Journal of Nutrition","year":2019,"pmid":"30418612","doi":"10.1093/jn/nxy194","type":"meta-analysis","finding":"Across 6 cohorts with 96,175 participants and 4,935 cases, ever skipping breakfast carried a relative risk of 1.33 for type 2 diabetes, 1.22 after adjustment for body-mass index, with the dose-response plateauing at 4 to 5 skipped days a week (1.55).","url":"https://pubmed.ncbi.nlm.nih.gov/30418612/"},{"id":"sievert2019","authors":"Sievert K, Hussain SM, Page MJ, et al.","title":"Effect of breakfast on weight and energy intake: systematic review and meta-analysis of randomised controlled trials","journal":"BMJ","year":2019,"pmid":"30700403","doi":"10.1136/bmj.l42","type":"meta-analysis","finding":"Across 13 randomized trials, participants assigned to eat breakfast ended 0.44 kg heavier than those assigned to skip it and ate 259.79 kcal a day more; all trials were at high or unclear risk of bias with short follow-up, and the authors caution against recommending breakfast for weight loss.","url":"https://pubmed.ncbi.nlm.nih.gov/30700403/"},{"id":"fong2017","authors":"Fong M, Caterson ID, Madigan CD","title":"Are large dinners associated with excess weight, and does eating a smaller dinner achieve greater weight loss? A systematic review and meta-analysis","journal":"British Journal of Nutrition","year":2017,"pmid":"28967343","doi":"10.1017/S0007114517002550","type":"meta-analysis","finding":"Across 10 observational studies, four found large evening intake associated with higher body-mass index, five found none and one the reverse (pooled P = 0.06); across five trials, smaller dinners produced a nonsignificant 0.89 kg more weight loss (minus 2.52 to 0.75), with high heterogeneity and risk of bias.","url":"https://pubmed.ncbi.nlm.nih.gov/28967343/"},{"id":"gan2015","authors":"Gan Y, Yang C, Tong X, et al.","title":"Shift work and diabetes mellitus: a meta-analysis of observational studies","journal":"Occupational and Environmental Medicine","year":2015,"pmid":"25030030","doi":"10.1136/oemed-2014-102150","type":"meta-analysis","finding":"Across 12 studies with 226,652 participants and 14,595 cases, ever working shifts carried pooled adjusted odds of 1.09 for diabetes, 1.37 in men and 1.09 in women, with rotating shifts carrying higher risk than other schedules.","url":"https://pubmed.ncbi.nlm.nih.gov/25030030/"},{"id":"leung2020","authors":"Leung GKW, Huggins CE, Ware RS, Bonham MP","title":"Time of day difference in postprandial glucose and insulin responses: Systematic review and meta-analysis of acute postprandial studies","journal":"Chronobiology International","year":2020,"pmid":"31782659","doi":"10.1080/07420528.2019.1683856","type":"meta-analysis","finding":"Across 15 acute studies (10 pooled) in healthy adults given an identical meal by day and by night, the postprandial glucose response was lower in the day (standardized mean difference minus 1.66) and the insulin response lower in the day (minus 0.35); glucose tolerance is poorer at night.","url":"https://pubmed.ncbi.nlm.nih.gov/31782659/"},{"id":"moon2020","authors":"Moon S, Kang J, Kim SH, et al.","title":"Beneficial Effects of Time-Restricted Eating on Metabolic Diseases: A Systemic Review and Meta-Analysis","journal":"Nutrients","year":2020,"pmid":"32365676","doi":"10.3390/nu12051267","type":"meta-analysis","finding":"Across 19 studies, time-restricted eating lowered body weight by 0.90 kg and fat mass by 1.58 kg with fat-free mass preserved, systolic pressure by 3.07 mm Hg, fasting glucose by 2.96 mg/dL and triglycerides by 11.60 mg/dL.","url":"https://pubmed.ncbi.nlm.nih.gov/32365676/"},{"id":"liul2022","authors":"Liu L, Chen W, Wu D, Hu F","title":"Metabolic Efficacy of Time-Restricted Eating in Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials","journal":"Journal of Clinical Endocrinology and Metabolism","year":2022,"pmid":"36190980","doi":"10.1210/clinem/dgac570","type":"meta-analysis","finding":"Across 17 randomized trials with 899 participants and at least 4 weeks of time-restricted eating, weight fell 1.60 kg and fat mass 1.48 kg; in participants with overweight, triglycerides fell 12.71 mg/dL, total cholesterol 6.45 and LDL cholesterol 7.0; no significant effect on waist, body-mass index, HbA1c or blood pressure.","url":"https://pubmed.ncbi.nlm.nih.gov/36190980/"},{"id":"pellegrini2020","authors":"Pellegrini M, Cioffi I, Evangelista A, et al.","title":"Effects of time-restricted feeding on body weight and metabolism. A systematic review and meta-analysis","journal":"Reviews in Endocrine and Metabolic Disorders","year":2020,"pmid":"31808043","doi":"10.1007/s11154-019-09524-w","type":"meta-analysis","finding":"Across 11 studies (5 randomized, 6 observational, most of Ramadan fasting) with 485 participants and fasts of 12 to 20 hours over 4 to 8 weeks, time-restricted feeding lowered weight by 1.07 kg and fasting glucose by 1.71 mg/dL; observational studies showed an inverse association with fat-free mass (minus 1.33 kg).","url":"https://pubmed.ncbi.nlm.nih.gov/31808043/"},{"id":"stonge2017","authors":"St-Onge MP, Ard J, Baskin ML, et al.; American Heart Association","title":"Meal Timing and Frequency: Implications for Cardiovascular Disease Prevention: A Scientific Statement From the American Heart Association","journal":"Circulation","year":2017,"pmid":"28137935","doi":"10.1161/CIR.0000000000000476","type":"consensus","finding":"Reviews breakfast skipping, intermittent fasting, meal frequency and timing of eating occasions; proposes research definitions for meals, snacks and eating occasions; finds irregular eating patterns less favorable for cardiometabolic health; recommends intentional eating with attention to timing and frequency; sets no number.","url":"https://pubmed.ncbi.nlm.nih.gov/28137935/"},{"id":"evert2019","authors":"Evert AB, Dennison M, Gardner CD, et al.","title":"Nutrition Therapy for Adults With Diabetes or Prediabetes: A Consensus Report","journal":"Diabetes Care","year":2019,"pmid":"31000505","doi":"10.2337/dci19-0014","type":"consensus","finding":"The consensus report for the American Diabetes Association reviews intermittent fasting among eating patterns, cites the early-window trial in men with prediabetes, and states that the safety of intermittent fasting in people with special health situations, including pregnancy and disordered eating, has not been studied.","url":"https://pubmed.ncbi.nlm.nih.gov/31000505/"},{"id":"manoogian2022","authors":"Manoogian ENC, Chow LS, Taub PR, Laferrère B, Panda S","title":"Time-restricted Eating for the Prevention and Management of Metabolic Diseases","journal":"Endocrine Reviews","year":2022,"pmid":"34550357","doi":"10.1210/endrev/bnab027","type":"review","finding":"Defines time-restricted eating as all calorie intake within a consistent interval of less than 12 hours without overtly attempting to reduce calories, traces it to peripheral circadian clocks that respond to nutrient timing, and states that pilot human studies are promising and that more clinical and mechanistic studies are needed.","url":"https://pubmed.ncbi.nlm.nih.gov/34550357/"},{"id":"chaix2019","authors":"Chaix A, Manoogian ENC, Melkani GC, Panda S","title":"Time-Restricted Eating to Prevent and Manage Chronic Metabolic Diseases","journal":"Annual Review of Nutrition","year":2019,"pmid":"31180809","doi":"10.1146/annurev-nutr-082018-124320","type":"review","finding":"Molecular clocks in almost every cell anticipate rhythmic nutrient availability; in the time-restricted eating paradigm daily caloric intake is confined to a consistent window of 8 to 12 hours.","url":"https://pubmed.ncbi.nlm.nih.gov/31180809/"},{"id":"poggiogalle2018","authors":"Poggiogalle E, Jamshed H, Peterson CM","title":"Circadian regulation of glucose, lipid, and energy metabolism in humans","journal":"Metabolism","year":2018,"pmid":"29195759","doi":"10.1016/j.metabol.2017.11.017","type":"review","finding":"Human studies report circadian rhythms in glucose, insulin, glucose tolerance, lipids, energy expenditure and appetite, several peaking in the biological morning or around noon, implicating earlier in the day as the better time to eat; misalignment from mistimed light, sleep or food impairs metabolism.","url":"https://pubmed.ncbi.nlm.nih.gov/29195759/"},{"id":"gill2015","authors":"Gill S, Panda S","title":"A Smartphone App Reveals Erratic Diurnal Eating Patterns in Humans that Can Be Modulated for Health Benefits","journal":"Cell Metabolism","year":2015,"pmid":"26411343","doi":"10.1016/j.cmet.2015.09.005","type":"cross-sectional","finding":"Healthy non-shift-working adults logging every ingestion for three weeks ate erratically, with under 25 percent of calories before noon and over 35 percent after 6 p.m.; the 95 percent intake duration exceeded 14 hours 45 minutes for half and only 9.7 percent ate within 12 hours; 8 overweight adults who shortened a 14-hour-plus window to 10 to 11 hours for 16 weeks lost 3.27 kg (0.91 to 5.62) with better sleep and energy, maintained at one year.","url":"https://pubmed.ncbi.nlm.nih.gov/26411343/"},{"id":"damiola2000","authors":"Damiola F, Le Minh N, Preitner N, Kornmann B, Fleury-Olela F, Schibler U","title":"Restricted feeding uncouples circadian oscillators in peripheral tissues from the central pacemaker in the suprachiasmatic nucleus","journal":"Genes and Development","year":2000,"pmid":"11114885","doi":"10.1101/gad.183500","type":"laboratory","finding":"In mice, restricting feeding time shifted the phase of circadian gene expression in peripheral tissues by up to 12 hours while the suprachiasmatic nucleus was unaffected; the liver reset fastest, and after a week of daytime feeding all peripheral tissues examined were in phase.","url":"https://pubmed.ncbi.nlm.nih.gov/11114885/"},{"id":"stokkan2001","authors":"Stokkan KA, Yamazaki S, Tei H, Sakaki Y, Menaker M","title":"Entrainment of the circadian clock in the liver by feeding","journal":"Science","year":2001,"pmid":"11161204","doi":"10.1126/science.291.5503.490","type":"laboratory","finding":"In transgenic rats whose tissues report clock activity by luminescence, restricted feeding shifted the liver's rhythm by 10 hours within 2 days while the suprachiasmatic nucleus stayed phase-locked to the light-dark cycle, suggesting peripheral clocks are coupled to the brain mainly through rhythmic behavior such as feeding.","url":"https://pubmed.ncbi.nlm.nih.gov/11161204/"},{"id":"hatori2012","authors":"Hatori M, Vollmers C, Zarrinpar A, et al.","title":"Time-restricted feeding without reducing caloric intake prevents metabolic diseases in mice fed a high-fat diet","journal":"Cell Metabolism","year":2012,"pmid":"22608008","doi":"10.1016/j.cmet.2012.04.019","type":"laboratory","finding":"Mice given a high-fat diet for 8 hours a day ate the same calories as mice with free access but were protected against obesity, hyperinsulinemia, hepatic steatosis and inflammation, with improved oscillations of the circadian clock and its target genes.","url":"https://pubmed.ncbi.nlm.nih.gov/22608008/"},{"id":"chaix2014","authors":"Chaix A, Zarrinpar A, Miu P, Panda S","title":"Time-restricted feeding is a preventative and therapeutic intervention against diverse nutritional challenges","journal":"Cell Metabolism","year":2014,"pmid":"25470547","doi":"10.1016/j.cmet.2014.11.001","type":"laboratory","finding":"In mice on several obesity-producing diets, time-restricted feeding (8 to 9 hours in the active phase) attenuated metabolic disease in proportion to the fasting duration, kept its protection when interrupted by free access at weekends, and stabilized and reversed established obesity and type 2 diabetes.","url":"https://pubmed.ncbi.nlm.nih.gov/25470547/"},{"id":"corley2018","authors":"Corley BT, Carroll RW, Hall RM, Weatherall M, Parry-Strong A, Krebs JD","title":"Intermittent fasting in Type 2 diabetes mellitus and the risk of hypoglycaemia: a randomized controlled trial","journal":"Diabetic Medicine","year":2018,"pmid":"29405359","doi":"10.1111/dme.13595","type":"rct","finding":"In 41 adults with type 2 diabetes on glucose-lowering medication following a 500 to 600 kcal diet on 2 days a week for 12 weeks, fasting raised the rate of hypoglycemia (rate ratio 2.05, 1.17 to 3.52) despite medication reduction, with no difference between consecutive and non-consecutive days; weight, HbA1c, fasting glucose and quality of life improved in both arms.","url":"https://pubmed.ncbi.nlm.nih.gov/29405359/"},{"id":"ganson2022","authors":"Ganson KT, Cuccolo K, Hallward L, Nagata JM","title":"Intermittent fasting: Describing engagement and associations with eating disorder behaviors and psychopathology among Canadian adolescents and young adults","journal":"Eating Behaviors","year":2022,"pmid":"36368052","doi":"10.1016/j.eatbeh.2022.101681","type":"cross-sectional","finding":"Among 2,762 Canadian adolescents and young adults, 47.7 percent of women, 38.4 percent of men and 52.0 percent of transgender and gender-nonconforming participants reported intermittent fasting in the past 12 months, and fasting was associated with eating-disorder psychopathology in all groups, most consistently in women.","url":"https://pubmed.ncbi.nlm.nih.gov/36368052/"}],"written":"2026-10-23","updated":"2026-10-23","reviewed":true,"reviewedOn":"2026-10-24","related":{"essays":[],"glossary":[],"symptoms":[],"entries":["sleep","fasting-insulin","fasting-glucose","hba1c","homa-ir","triglycerides","cortisol","fiber","protein-intake","resistance-training"]},"url":"https://taggehealth.com/labs/meal-timing","author":"Daniel Tagge, MD","publisher":"Tagge Health","license":"Free to read and cite with attribution to the URL above.","inPractice":"I do not prescribe an eating window as a number, because the evidence does not hand me one. What the trials show is that most of what a shortened window does to weight is to cut how much a person eats, and that a window on its own, with no other change, did little in the one trial that tested it that way. What interests me more is timing, and I read it through the markers rather than the clock. A fasting insulin that runs high next to a normal glucose, triglycerides that run high while LDL behaves, an HbA1c drifting up in someone who is not gaining weight, a cortisol curve that is flat in the morning: one marker is a clue, three are a story, and the story is often a day that ends late, with the biggest meal and the most carbohydrate landing in the hours when the body handles glucose worst. So before I say anything about a window I ask when the first and last calories happen on a workday and on a weekend, when the person sleeps and wakes, whether they are a morning or an evening type, how a shift roster falls, how they slept the week before the blood draw, and whether food rules have ever become a problem for them. If the answers point to late eating, the lever I reach for first is the last meal: earlier and smaller, with the day's protein and carbohydrate moved forward, and a consistent start and finish seven days a week. Then I retest insulin, glucose, triglycerides and, where it is relevant, cortisol and sleep, and let the numbers tell me whether it mattered for that person rather than assuming it did. There are people I will not put on a fasting window: anyone pregnant or breastfeeding, anyone with a history of an eating disorder, an older adult who is underweight or losing muscle, and anyone on insulin or a sulfonylurea unless we have adjusted the doses first, because in a trial fasting doubled hypoglycemia on those drugs even with the doses reduced. I will say plainly where I am ahead of the evidence. The case for eating early rests mostly on one five-week study in eight men, on a handful of trials lasting weeks, and on the physiology of evening glucose handling and melatonin, which is good physiology but not an outcome trial; no study has shown that moving dinner forward prevents a heart attack. I act on it anyway when the markers and the schedule line up, and I say so."}