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Time-restricted5 human studies cited

14:10 Time-Restricted Eating

14 hours without food · Daily

Written by Reviewed Sep 2026

Also called: 10-hour eating window, Personalised TRE

A 10-hour eating window, usually shortened from a habitual 14 hours or more. It is the window with the strongest cardiometabolic results in people who already had metabolic disease, and the one where the lean mass split came out most favourably.

Overview

The 10-hour window has been studied mainly by the Panda group at the Salk Institute and by Wilkinson at the University of California San Diego, in adults with metabolic syndrome or obesity who were eating across 14 hours or more before they started. In that population the intervention is not really a fast, it is a 4-hour reduction in the daily eating span.

That framing matters when reading the results. TIMET participants had a baseline eating window of 14.19 hours and were required to shorten it by at least 4 hours. They did so by pushing the start 1 hour 49 minutes later after waking and the end 2 hours 50 minutes earlier before bedtime, so both ends moved.

What this window produced in trials was a small HbA1c change, a measurable reduction in glucose variability, weight loss that was mostly fat, and blood pressure and LDL improvements in people who were already on statins and antihypertensives and stayed on them.

How it works

Pick a consistent 10-hour window and log every caloric intake. TIMET personalised the window to each participant rather than assigning a clock time, with the only requirement being a reduction of at least 4 hours from baseline, and used the myCircadianClock app for real-time logging. Wilkinson's earlier single-arm study used a consistent self-selected 10-hour window.

Adherence in both was high and was measured rather than assumed: 11.6% of days in TIMET had a caloric entry more than 15 minutes outside the window, so more than 85% of days were on protocol, and logging adherence in the 2020 study was 85.61% during the intervention.

Pharmacotherapy was allowed and continued in TIMET. This was tested as something added on top of standard care, not as a replacement for it.

What 14 hours actually reaches

What was measured at 10 hours is a modest glycaemic effect and a larger effect on glucose variability. TIMET found HbA1c falling 0.10% relative to standard of care (95% CI -0.19% to -0.003%) from a baseline of 5.87%, and continuous glucose monitoring showed intra-day variability down 7.7% and inter-day variability down 14.1% between groups, which were the largest between-group changes in the trial. A 14-hour fast is the shortest window on this page and reaches the least. No autophagy or mitophagy measurement has been made in a person on a 10-hour eating window, and nothing in the record supports describing this window in terms of a cellular recycling threshold. What it does reach, on the measurements available, is the overnight and morning glucose profile and blood pressure. The honest comparison point is the 12-hour window, which functions in this literature as the comparator rather than the treatment. The one pragmatic randomised trial that prescribed 12 hours in 54 adults produced 1.6% weight loss against 1.1% for standard dietary advice, a between-group difference of 0.88% that was not significant (p = 0.43).

Fig. 1 · what has been measured, hour by hour
  1. 0h to 4h

    Still absorbing

    Burning
    Glucose from the meal just eaten, with insulin high enough to hold fat release down
    • Insulin is at its post-meal peak, and while it is there, adipose tissue lipase stays suppressed and fat is being stored rather than released.
    • The hour count on most fasting charts starts at the last bite. Absorption of a mixed meal is still running here, so the clock and the physiology are not yet the same thing.

    Read the biologyInsulin and insulin sensitivity during a fast

    Measured in people
    The human hour-by-hour fasting series begin later than this. Klein 1993 took its first sample at 12 hours in 6 healthy men, and Rothman 1991 reports its first gluconeogenesis figure as an average across the first 22 hours. This row is the fed state those measurements are compared against, and no extended-fasting measurement exists inside it.

  2. 4h to 12h

    Post-absorptive

    Burning
    A mix of remaining glucose and fatty acids, with the liver covering the brain's glucose demand
    Blood glucose
    5.58 ± 0.08 mmol/L (100.5 mg/dL) at the 12 hour mark, in 6 healthy men
    Ketones (BHB)
    Total ketone bodies around 0.20 mmol/L in overnight-fasted subjects. That figure is acetoacetate plus beta-hydroxybutyrate, not BHB on its own.
    Insulin
    64.6 ± 12.9 pmol/L (9.3 microunits/mL) at 12 hours, in the same 6 men
    • Glycerol release runs at 2.08 ± 0.22 and palmitic acid release at 1.63 ± 0.20 micromol/kg/min at 12 hours. Those are the numbers everything later in the fast is measured against.
    • Gluconeogenesis is already the majority contributor to glucose production rather than a reserve waiting to be called on, which is the first place the popular switch model breaks.

    Read the biologyInsulin and insulin sensitivity during a fastGlycogen depletion and gluconeogenesis

    Measured in people
    Klein 1993 measured glucose, insulin and stable-isotope lipid kinetics at 12 hours in 6 healthy men. Féry 1983 measured total ketone body turnover in overnight-fasted subjects and put the baseline at 0.20 mmol/L. Rothman 1991 measured hepatic glycogen serially by 13C nuclear magnetic resonance through a 68 hour fast in healthy adults and calculated that gluconeogenesis supplied 64 ± 5% of total glucose production across the first 22 hours.

  3. 12h to 18h

    Ketones have not moved yet

    Burning
    Fatty acids rising, with glucose production increasingly made rather than released from store
    Ketones (BHB)
    Median change of 0% between 12 and 18 hours, sampled every 6 hours in 34 adults
    • Beta-hydroxybutyrate does not move in this window. In 34 adults sampled every 6 hours through the standard diagnostic 72 hour fast, the median change from 12 to 18 hours was zero.
    • Gluconeogenesis is supplying 64 ± 5% of glucose production across the first 22 hours, confirmed by an orthogonal method at about 47% by 14 hours. Glucose production does not switch from glycogen to fat at a threshold hour.
    • Whole blood LC3A messenger RNA was 22 ± 5% higher at 18 hours than in a 12 hour control arm in 11 overweight adults (p = 0.001). In the same subjects MTOR expression also rose, by 9 ± 3%.

    Read the biologyGlycogen depletion and gluconeogenesisKetogenesis and beta-hydroxybutyrateAutophagy

    Measured in people
    Service 2005 measured beta-hydroxybutyrate every 6 hours in 34 adults whose 72 hour fasts were negative for insulinoma. Rothman 1991 measured the gluconeogenic share by 13C NMR. Jamshed 2019 measured whole blood messenger RNA in an 11-person 4 day randomised crossover of an 08:00 to 14:00 eating window against 08:00 to 20:00. That is one gene's expression in blood cells, not autophagic flux and not muscle. No study in any species has tested a 16 hour timepoint for autophagy.

  4. 18h to 1d

    The steepest hours for fat release

    past this window
    Burning
    Fatty acids and glycerol, with ketone production starting its climb
    Ketones (BHB)
    Climbing. The median rise from 18 to 36 hours was +333%, the steepest proportional stretch of a 72 hour fast.
    Insulin
    70% of the entire decline seen across a 72 hour fast has already happened by 24 hours
    • The largest single interval increase in lipolysis across a whole 72 hour fast falls between 18 and 24 hours, and 60% of the total rise in lipid kinetics happens between 12 and 24 hours. The authors attribute that to the falling insulin rather than to any change in glucose.
    • Growth hormone was significantly higher after a 24 hour water-only fast than after a fed day in a randomised crossover of 30 healthy adults (p = 1.1 x 10^-4). The size of that rise is not in the accessible record and is not published here.
    • Haemoglobin, red cell count and haematocrit all rose together at 24 hours in the same trial. That combination is the signature of plasma volume contraction, not of new red cells.
    • 24 hour energy expenditure measured in a whole-room calorimeter fell during 24 hour fasting in 20 volunteers, with the size of the fall varying between individuals.

    Read the biologyInsulin and insulin sensitivity during a fastThe growth hormone responseKetogenesis and beta-hydroxybutyrateAutophagy

    Measured in people
    Horne 2013 randomised 30 apparently healthy adults to a 24 hour water-only fast or a day of usual eating in crossover and measured growth hormone, blood counts, cholesterol, triglycerides, bicarbonate and weight. Klein 1993 measured the lipid kinetics by stable isotope tracer. Hollstein 2020 measured 24 hour energy expenditure by whole-room calorimetry in 20 volunteers; the exact percentage decrease is not in the accessible record and is not published here. On autophagy, a 24 hour fast raised p62/SQSTM1 in the vastus lateralis of 50 women, which is movement in the direction of less autophagic degradation rather than more.

  5. 1d to 36h

    Thyroid drops before metabolic rate does

    past this window
    Burning
    Fat, with the remaining glucose built from glycerol, lactate and amino acids
    Ketones (BHB)
    1.308 ± 1.053 mmol/L after day 1 in 13 men beginning a 10 day water fast, from a baseline of 0.177 ± 0.044. The spread on that mean is as wide as the mean.
    • Gluconeogenesis supplies 82 ± 5% of glucose production between 22 and 36 hours.
    • Serum T3 fell from 2.30 ± 0.06 to 1.84 ± 0.03 nmol/L by 30 hours in 8 healthy men (p < 0.01), TSH fell below 1 mU/L and the nocturnal TSH peak was abolished. Serum cortisol did not differ across conditions.
    • Thyroid suppression therefore begins inside the first 30 hours, well before any measurable fall in resting metabolic rate.
    • Sodium excretion has not turned yet. In 9 obese women fasting with pre-fast salt intake maintained, urinary sodium began to rise after roughly 48 hours and then exceeded intake.

    Read the biologyGlycogen depletion and gluconeogenesisKetogenesis and beta-hydroxybutyrateAutophagy

    Measured in people
    Rothman 1991 measured the gluconeogenic share by 13C NMR in healthy adults. Hugues 1984 fasted 8 healthy men for 30 hours with serial thyroid sampling. Dai 2022 measured blood beta-hydroxybutyrate daily in 13 men fasting in a controlled facility. Sigler 1975 collected urine in 3 hour blocks from 9 obese women on a metabolic ward. On autophagy, the only human study with several within-fast timepoints took vastus lateralis biopsies at 2, 12, 24 and 36 hours: LC3I, LC3II and p62 all fell, in untrained subjects only, which the authors summarise as skeletal muscle autophagy being only modestly affected by 36 hours of fasting.

Human evidence

One randomised trial in metabolic syndrome with HbA1c as the primary outcome, one randomised trial in obesity with weight as the primary outcome, and one single-arm study that generated the hypothesis for both. All measured adherence directly rather than by recall alone.

  • Manoogian 2024, the TIMET trial, 121 randomised and 108 completed, 3 months, adults with metabolic syndrome and elevated fasting glucose or HbA1c, on top of standard-of-care counselling and continued medication. HbA1c fell 0.10% versus standard of care (95% CI -0.19% to -0.003%). Weight fell 2.98 kg versus 1.32 kg, a between-group difference of 1.66 kg. Diastolic blood pressure fell 3.98 mmHg within group and LDL cholesterol fell relative to standard of care. No major adverse events (Annals of Internal Medicine, 2024).
  • Wilkinson 2026, the TREAD trial, 61 randomised and 52 completed, 12 weeks, adults with obesity and a baseline eating window of 14 hours or more. Weight fell 4.59 kg (95% CI -5.51 to -3.67) versus 1.68 kg on standard-of-care counselling, a between-group difference of 2.91 kg (P < 0.001), and the loss was primarily body fat. Exploratory RNA sequencing of subcutaneous adipose tissue showed downregulation of proinflammatory genes, which is a mechanistic observation and not a clinical outcome (Obesity, 2026).
  • Wilkinson 2020, single-arm and not randomised, 35 enrolled and 19 analysed, 12 weeks in patients with metabolic syndrome, most of them on a statin, an antihypertensive or both. Weight fell 3.3 kg, systolic blood pressure 5.12 mmHg (P = 0.041), diastolic 6.47 mmHg (P = 0.004), LDL cholesterol 11.9 mg/dL and total cholesterol 13.2 mg/dL. HbA1c across the whole group fell 0.14% (P = 0.058); in the 12 participants with a baseline HbA1c of 5.7% or above it fell 0.22% (P = 0.04). There is no control arm, so all of this is within-subject change alongside continuing medical care (Cell Metabolism, 2020).
  • Continuous glucose monitoring in TIMET: CONGA, a measure of intra-day variability, differed between groups by 1.53 arbitrary units (95% CI -3.00 to -0.06), a 7.7% difference, and MODD, inter-day variability, by 0.13 mmol/L (95% CI -0.22 to -0.05), a 14.1% difference. This is the largest glycaemic variability result in the randomised time-restricted eating literature.

What this does not tell you: TIMET ran 3 months and TREAD 12 weeks, so neither speaks to durability. Diet was self-reported in both. TIMET's HbA1c effect was 0.10% from an already near-normal baseline, which is a genuine result and a small one. The 2020 study has no control arm at all. Body composition in TIMET was a secondary outcome in 108 completers, not a powered endpoint.

Reading the research record

The 10-hour window sits in an awkward place in the argument about whether time restriction does anything beyond calorie reduction, because in this population the comparator arm was standard-of-care dietary counselling rather than a matched calorie prescription. TIMET and TREAD both show separation from standard care. Neither is a test of the window against an equal calorie deficit, which is the design that produced the Liu 2022 null result at 8 hours.

There is also a genuine disagreement about whether shorter is better. Cienfuegos 2020 found 4-hour and 6-hour windows producing identical weight loss, which suggests the marginal hour stops paying at some point. Oldenburg 2025 found a self-selected 8-hour prescription drifting out to 9.8 hours and producing no separation from unrestricted eating. Read alongside TIMET's 10-hour window producing clear separation from standard care in a population starting at 14.19 hours, the pattern is more consistent with the size of the reduction from habit than with the absolute length of the window, although no trial has been designed to test that directly.

The research groups behind these trials are also the signatories of the published rebuttal to the NHANES eating-duration mortality analysis discussed on the 5:2 and alternate-day pages, and several report industry relationships in that paper's competing-interests statement. That is context for reading the field, not a reason to discount the measurements.

What happens to muscle

TIMET is the trial that reported the most favourable lean mass split in this literature, and it did so explicitly. Of the 2.98 kg mean weight loss in the TRE arm, 2.24 kg, approximately 75%, was fat mass, and approximately 0.28 kg, about 9%, was lean mass. Total fat mass fell 2240.22 g (95% CI -3044.43 to -1376.01), a 6.7% reduction, against 409.11 g in standard of care, a between-group difference of 1801.11 g. The authors noted directly that this contrasts with trials where time-restricted eating participants lost disproportionately more lean mass.

That 9% figure sits at the opposite end of the range from TREAT's approximately 65% at an 8-hour window. Both were DXA, both were secondary outcomes, and neither trial was powered as a body composition study. TREAT measured 50 people over 12 weeks; TIMET measured 108 over 3 months.

The two differences most likely to matter are population and window length. TIMET's participants had a mean age of 59 and metabolic syndrome and were shortening a 14-hour habit by 4 hours. TREAT's were younger and shortening much further, with protein intake not measured at all. The protein research is consistent on which lever moves this: trials that ran 1.6 to 2.2 g/kg/day with resistance training preserved lean mass regardless of window length, and the one trial run at 1.0 g/kg/day lost more of it. Neither TIMET nor TREAT reported protein in g/kg/day, so this remains an explanation the trials are consistent with rather than one they tested.

Doing it

Measure your current window first
TIMET required a reduction of at least 4 hours from baseline and its participants started at 14.19 hours. Somebody already eating across 11 hours is doing a different intervention from somebody starting at 15.
Log it, do not estimate it
Both Salk group trials used real-time app logging and reported adherence as a measured number. Trials that let people self-select without logging drifted: Oldenburg's 8-hour arm achieved 9.8 hours.
Protein target
Neither TIMET nor TREAD reported protein in g/kg/day. Across the wider literature, lean mass was preserved in trials running 1.6 to 2.2 g/kg/day and fell further in the one trial run at 1.0 g/kg/day, so this is the number worth tracking inside a 10-hour window.
Medication stays
TIMET allowed and continued pharmacotherapy, so its results describe time restriction added to standard care. Blood pressure medication in particular stacks with an effect that is already happening, since fasting lowers blood pressure through reduced insulin, sodium loss and glycogen-bound water release.
Where the strongest signal was
Glucose variability, not weight. The between-group CGM differences of 7.7% intra-day and 14.1% inter-day were the largest changes in TIMET alongside HbA1c.

Breaking the fast

A 14-hour overnight fast ends in the ordinary way, and no trial in this section prescribed a first meal. The relevant physiology is that postabsorptive myofibrillar protein synthesis in healthy adults sits around 0.03 to 0.05 %/h and does not differ between young and old, so an overnight fast has not switched protein synthesis off, it has removed the feeding-induced rise. Older adults need a larger per-meal protein dose to produce that rise, with 40 g beating 20 g after exercise in men around 71.

Citations

  1. Human2024
    Time-Restricted Eating in Adults With Metabolic Syndrome: A Randomized Controlled Trial

    Annals of Internal Medicine

    121 randomised, 108 completed, 3 months of personalised 8 to 10 hour eating plus standard-of-care counselling versus standard of care alone in metabolic syndrome. HbA1c -0.10% (95% CI -0.19% to -0.003%). Weight -2.98 kg versus -1.32 kg, between-group -1.66 kg. Of that loss, 2.24 kg (about 75%) was fat and 0.28 kg (about 9%) lean. CGM intra-day variability -7.7% and inter-day -14.1% between groups. Adherence above 85% of days. No major adverse events.

  2. Human2026
    Time-Restricted Eating Promotes Weight Loss and Favorable Changes in Adipose in Obesity: The TREAD Randomized Control Trial

    Obesity (Silver Spring)

    61 randomised, 52 completed, 12 weeks of a 10-hour window versus standard-of-care dietary counselling in adults with obesity and a baseline window of 14 hours or more. Weight -4.59 kg (95% CI -5.51 to -3.67) versus -1.68 kg, between-group -2.91 kg (P < 0.001), loss primarily body fat. Exploratory adipose RNA sequencing showed downregulation of proinflammatory genes.

  3. Human2020
    Ten-Hour Time-Restricted Eating Reduces Weight, Blood Pressure, and Atherogenic Lipids in Patients with Metabolic Syndrome

    Cell Metabolism

    Single-arm, not randomised. 35 enrolled, 19 analysed, 12 weeks. Weight -3.3 kg, systolic -5.12 mmHg (P = 0.041), diastolic -6.47 mmHg (P = 0.004), LDL -11.9 mg/dL, total cholesterol -13.2 mg/dL. HbA1c -0.14% overall (P = 0.058) and -0.22% (P = 0.04) in the 12 participants with baseline HbA1c at or above 5.7%. Logging adherence 85.61%. No control arm.

  4. Human2021
    The Effects of Time-Restricted Eating versus Standard Dietary Advice on Weight, Metabolic Health and the Consumption of Processed Food: A Pragmatic Randomised Controlled Trial in Community-Based Adults

    Nutrients

    54 adults with a baseline eating duration above 14 hours and at least one metabolic syndrome component, 6 months of a 12-hour window versus standard dietary advice. TRE lost 1.6% of initial body weight (SD 2.9, p = 0.01) and standard advice 1.1% (not significant), with a between-group difference of 0.88% that was not significant (p = 0.43). The reference point for how little a 12-hour window moves on its own.

  5. Human2020
    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

    JAMA Internal Medicine

    Cited here as the lean mass counterpoint. In the 50-person DXA subgroup an 8-hour window produced 1.70 kg of weight loss of which 1.10 kg was lean mass, approximately 65%, against TIMET's approximately 9% at a 10-hour window. Both were DXA, both secondary outcomes, neither powered for body composition.

What people report

These are uncontrolled self-reports, not evidence. They are here because they tell you what to expect and what to watch for, which the trial literature does not. They cannot tell you whether anything works.

  • Easier to sustain than a shorter window, because breakfast survives
  • Both ends of the window moving, later start and earlier finish, rather than one
  • Better sleep timing as the last meal moves away from bedtime
  • Small early weight change that continues slowly rather than stopping

Sources: Uncontrolled self-report. These are behaviours and impressions logged by participants inside the trials cited here, including the measured 1 hour 49 minute later start and 2 hour 50 minute earlier finish in TIMET, not community survey data. A separate review of what fasting communities report is still being compiled and nothing here is drawn from it.

Who this is wrong for

  • Anyone taking an SGLT2 inhibitor without a prescriber stopping it first, because of the risk of ketoacidosis at a normal-looking glucose reading.
  • Anyone on insulin, a sulfonylurea or a meglitinide whose dose has not been reviewed against a shortened intake window.
  • Pregnancy and breastfeeding, where the glucose demand is continuous and where dieting to lose weight was the precipitant in 76% of 18 reported cases of lactation ketoacidosis.
  • Anyone with a history of an eating disorder or current loss-of-control eating.
  • Children and adolescents, where no long-term growth or development follow-up exists.
  • Anyone with a BMI under 18.5 or meeting the NICE refeeding risk criteria.
  • Anyone whose work schedule makes a consistent window impossible, since consistency rather than length is what the trials in this section actually delivered. A trial of personalised 10-hour eating in shift workers is running at the Salk Institute with a primary completion date of August 2028.

Questions

Is a 10-hour window long enough to do anything?
In people who were eating across 14 hours or more, yes, measurably. TIMET lowered HbA1c by 0.10% relative to standard care, cut intra-day glucose variability by 7.7% and inter-day by 14.1%, and produced 1.66 kg more weight loss over 3 months. TREAD produced 2.91 kg more weight loss than counselling alone over 12 weeks. Whether the same window helps somebody already eating across 11 hours has not been tested.
Why did this window preserve lean mass better than shorter ones?
TIMET reported about 9% of its weight loss as lean mass and TREAT reported about 65% at an 8-hour window, but the trials differed in population, duration and unmeasured protein intake as well as in window length. The protein literature points at intake rather than the window: trials at 1.6 to 2.2 g/kg/day preserved lean mass at 8 hours, and the one run at 1.0 g/kg/day did not. Neither TIMET nor TREAD reported protein in g/kg/day.
Does it matter where in the day the 10 hours sit?
TIMET personalised the window rather than fixing a clock time, and its participants moved both ends, starting 1 hour 49 minutes later after waking and finishing 2 hours 50 minutes earlier before bed. A separate crossover trial comparing early and delayed 9-hour windows in 15 men found no difference between the two conditions on any variable, although only the early condition lowered mean fasting glucose against its own baseline.