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Fasting · September 30, 2026 · Memios · 14 min read

16:8 time-restricted eating

Evidence is limited and largely points to no advantage over ordinary calorie restriction. In TREAT (116 adults, 12 weeks) 16:8 eating was no better than three structured meals for weight (-0.26 kg difference.

16:8 time-restricted eating16:8 intermittent fasting8-hour eating windowLeangainsfasting research
Photograph for 16:8 time-restricted eating: a calm table with an empty plate and a glass of water in morning light.

TLDR

  • Limited evidence. Evidence is limited and largely points to no advantage over ordinary calorie restriction. In TREAT (116 adults, 12 weeks) 16:8 eating was no better than three structured meals for weight (-0.26 kg difference, P = .63) and was linked to a loss of appendicular lean mass.
  • What it is: All food is eaten within an 8-hour window each day (in the TREAT trial, 12:00 pm to 8:00 pm) and nothing with calories is taken for the other 16 hours.
  • Main use, supported: In a 6-month trial in adults with type 2 diabetes, noon-to-8 pm eating reduced weight relative to control, lowered HbA1c by the same amount as calorie restriction, and no serious adverse events were reported.
  • Claim NOT supported by research: A network meta-analysis of 99 trials found alternate-day fasting gave slightly more weight loss than time-restricted eating, and time-restricted eating gave no weight benefit over continuous energy restriction. (moderate certainty)
  • Another claim NOT supported: The 2026 Cochrane review found intermittent fasting, including time-restricted feeding, made little to no difference to weight loss compared with regular dietary advice. (low certainty)
  • What goes wrong: 4 findings on harm. In the in-person subgroup of TREAT, the 16:8 group lost more appendicular lean mass than the three-meal group.
  • Be careful if you are: people taking insulin or other glucose-lowering (antihyperglycaemic) medicines; older adults and anyone concerned about muscle loss; people with a history of eating disorders; people with heart disease or cancer.
  • Common myth: 16:8 burns more fat than a normal diet with the same calories.

What it is

All food is eaten within an 8-hour window each day (in the TREAT trial, 12:00 pm to 8:00 pm) and nothing with calories is taken for the other 16 hours. Some trials leave calories unrestricted within the window; others combine the window with a calorie-restricted diet.

What the research says

Evidence is limited and largely points to no advantage over ordinary calorie restriction. In TREAT (116 adults, 12 weeks) 16:8 eating was no better than three structured meals for weight (-0.26 kg difference, P = .63) and was linked to a loss of appendicular lean mass. In a 12-month trial in China (139 adults) an 8-hour window plus calorie restriction was no better than calorie restriction alone (-1.8 kg difference, P = .11). A 12-month trial in Chicago found noon-to-8 pm eating beat a control group but not 25% calorie restriction. In type 2 diabetes a 6-month trial found weight and HbA1c fell versus control, with no difference from calorie restriction on HbA1c and no serious adverse events. Meta-analyses find time-restricted eating reduces weight versus no restriction, adds nothing to calorie restriction, reduces fat-free mass, and is outperformed by alternate-day fasting. An unreviewed 2024 conference abstract associated eating in under 8 hours with higher cardiovascular death, but experts disputed its methods.

Evidence grade: Limited evidence.

The schedule

  • Pattern: daily
  • Fasting hours: 16
  • Eating hours: 8

Why people choose it

People pick 16:8 because it needs no calorie counting: in trials, eating from noon to 8 pm produced weight loss compared with no change in eating habits. But in the head-to-head trials that matter most it did not beat ordinary daily calorie restriction, either on its own over 12 months or added to calorie restriction over 12 months. A meta-analysis found adding it to calorie restriction gave no additional weight loss, and a 12-week trial found a small loss of lean mass.

Cautions

  • people taking insulin or other glucose-lowering (antihyperglycaemic) medicines: A 2026 meta-analysis of time-restricted eating in type 2 diabetes said that for patients taking antihyperglycaemic agents, blood glucose should be closely monitored and medicines adjusted in good time, both to prevent hypoglycaemia and because moving meal times can disrupt usual dosing. It did not name specific drug classes in that passage. (Source 1)
  • older adults and anyone concerned about muscle loss: In TREAT the 16:8 group lost more appendicular lean mass than the three-meal group, and TREAT enrolled no one over 64. (Source 2)
  • people with a history of eating disorders: The Cochrane team warned its fasting results may not apply to people with underlying eating disorders or behaviours; a review of time-restricted eating studies also found higher bedtime hunger and, in interviews, fear of hunger. (Source 3)
  • people with heart disease or cancer: In the unreviewed 2024 conference abstract, the association with cardiovascular death was also seen in people living with heart disease or cancer. This is an unconfirmed observational signal. (Source 4)
  • people at a healthy or low body weight: The main trials enrolled adults with overweight or obesity (TREAT: BMI 27 to 43); people at a lower weight were not studied. (Source 2)

What goes wrong

In the in-person subgroup of TREAT, the 16:8 group lost more appendicular lean mass than the three-meal group. (Source 2)

  • Randomized trial, Certainty not rated.
  • Size: 50 in the in-person cohort (25 per group)
  • Who: adults with overweight or obesity living near San Francisco.
  • How long: 12 weeks.
  • Result: Appendicular lean mass index difference -0.16 kg/m2 (95% CI -0.27 to -0.05; P = .005)
  • Funding: independent: NIH grants R01 DK109008, P30 DK098722 and M01 RR001271 (NIDDK/NCRR), as listed in the Europe PMC grant record.

Limit of this finding: Secondary outcome in a small subgroup.

There was also a significant difference in appendicular lean mass index between groups (-0.16 kg/m2; 95% CI, -0.27 to -0.05; P = .005).

The same meta-analysis found time-restricted eating reduced fat-free mass, both alone and combined with energy restriction. (Source 5)

  • Meta-analysis, Certainty not rated.
  • Size: 1,242 participants in 20 RCTs.
  • Who: adults.
  • How long: varied.
  • Result: TRE WMD -0.58 kg (95% CI -0.81 to -0.36); TRE+ER WMD -0.56 kg (95% CI -0.81 to -0.31)
  • Funding: not stated.

Both TRE and TRE + ER decreased fat-free mass (TRE = WMD:-0.58 kg, 95%CI:-0.81 to -0.36, p < 0.00001; TRE + ER = WMD:-0.56 kg, 95%CI:-0.81 to -0.31, p < 0.0001).

In the same network meta-analysis, time-restricted eating produced a small rise in total and LDL cholesterol compared with whole-day fasting. (Source 6)

  • Meta-analysis, Certainty not rated.
  • Size: 6,582 adults in 99 randomised trials.
  • Who: adults.
  • How long: most trials under 24 weeks.
  • Result: Small increase in total, LDL and non-HDL cholesterol vs whole-day fasting (numbers not in the recorded abstract)
  • Funding: NIDDK grant P30 DK056336 listed in the Europe PMC record (not checked against the paper)

Compared with whole day fasting, however, time restricted eating resulted in a small increase in total cholesterol, low density lipoprotein cholesterol, and non-high density lipoprotein cholesterol.

In an unreviewed 2024 conference abstract using US survey data, eating all food within less than 8 hours a day was associated with a 91% higher risk of cardiovascular death. (Source 7)

  • Cohort study, Certainty not rated.
  • Size: about 20,000 US adults, average age 49.
  • Who: NHANES 2003-2018 participants linked to National Death Index records through December 2019.
  • How long: follow-up to December 2019.
  • Result: 91% higher risk of cardiovascular death for <8-hour eating vs 12-16 hours; not associated with lower all-cause death.
  • Funding: not stated.

Limit of this finding: UNREVIEWED CONFERENCE ABSTRACT (AHA EPI|Lifestyle 2024, Abstract P192), not a peer-reviewed paper. Eating windows were estimated from two days of self-reported recall in a cross-sectional national survey, later linked to death records; the <8-hour group was about 2% of the sample. An association only; 34 fasting researchers publicly disputed the methods.

People who followed a pattern of eating all of their food across less than 8 hours per day had a 91% higher risk of death due to cardiovascular disease.

What the evidence supports

In a 6-month trial in adults with type 2 diabetes, noon-to-8 pm eating reduced weight relative to control, lowered HbA1c by the same amount as calorie restriction, and no serious adverse events were reported. (Source 8)

  • Randomized trial, Certainty not rated.
  • Size: 75 adults.
  • Who: adults aged 18 to 80 with obesity and type 2 diabetes (mean age 55, mean HbA1c 8.1%; 71% women; 53% non-Hispanic Black)
  • How long: 6 months.
  • Result: Weight -3.56% (95% CI -5.92% to -1.20%) vs control; HbA1c -0.91% (TRE) and -0.94% (CR) vs control, no difference between TRE and CR.
  • Funding: not stated.

Limit of this finding: Small; the authors say findings need confirmation in larger, longer trials.

Levels of HbA1c decreased in the TRE (-0.91% [95% CI, -1.61% to -0.20%]) and CR (-0.94% [95% CI, -1.59% to -0.30%]) groups, relative to controls, with no differences between the TRE and CR groups.

What the evidence does not support

In the 12-week TREAT trial, eating from noon to 8 pm was not more effective for weight loss than eating three structured meals a day. (Source 2)

  • Randomized trial, Certainty not rated.
  • Size: 116 adults.
  • Who: US adults aged 18 to 64 with BMI 27 to 43 (mean age 46.5; 60% men)
  • How long: 12 weeks.
  • Result: Between-group weight difference -0.26 kg (95% CI -1.30 to 0.78; P = .63); TRE within-group -0.94 kg (95% CI -1.68 to -0.20)
  • Funding: independent: NIH grants R01 DK109008, P30 DK098722 and M01 RR001271 (NIDDK/NCRR), as listed in the Europe PMC grant record.

Limit of this finding: Run through a mobile app with remote weighing; short.

Time-restricted eating, in the absence of other interventions, is not more effective in weight loss than eating throughout the day.

In a 12-month trial, an 8-hour eating window (8 am to 4 pm) plus calorie restriction produced no significantly greater weight loss than the same calorie restriction alone. (Source 9)

  • Randomized trial, Certainty not rated.
  • Size: 139 randomised; 118 (84.9%) completed.
  • Who: adults with obesity in China.
  • How long: 12 months.
  • Result: Weight -8.0 kg (95% CI -9.6 to -6.4) vs -6.3 kg (95% CI -7.8 to -4.7); net difference -1.8 kg (95% CI -4.0 to 0.4; P = 0.11)
  • Funding: independent (National Key Research and Development Project and others)

Limit of this finding: The window was 8 am to 4 pm, an early 8-hour window; both groups also cut calories to 1,200 to 1,800 kcal per day. The trial found no substantial differences between groups in the number of adverse events.

Changes in weight were not significantly different in the two groups at the 12-month assessment (net difference, -1.8 kg; 95% CI, -4.0 to 0.4; P = 0.11).

A network meta-analysis of 99 trials found alternate-day fasting gave slightly more weight loss than time-restricted eating, and time-restricted eating gave no weight benefit over continuous energy restriction. (Source 6)

  • Meta-analysis, Moderate certainty.
  • Size: 6,582 adults in 99 randomised trials.
  • Who: adults, healthy or with existing health conditions.
  • How long: most trials under 24 weeks.
  • Result: ADF vs TRE -1.69 kg (95% CI -2.49 to -0.88), moderate certainty.
  • Funding: NIDDK grant P30 DK056336 listed in the Europe PMC record (not checked against the paper)

Additionally, alternate day fasting showed a trivial reduction in body weight compared with both time restricted eating and whole day fasting (mean difference -1.69 kg (-2.49 to -0.88) and -1.05 kg (-1.90 to -0.19), respectively, both with moderate certainty of evidence).

The 2026 Cochrane review found intermittent fasting, including time-restricted feeding, made little to no difference to weight loss compared with regular dietary advice. (Source 10)

  • Systematic review, Low certainty.
  • Size: 21 studies, 1,430 participants for this outcome (the review holds 22 studies, 1,995 participants)
  • Who: adults with overweight or obesity.
  • How long: up to 12 months.
  • Result: MD -0.33% (95% CI -0.92 to 0.26) in percentage weight loss vs dietary advice.
  • Funding: independent (no dedicated funding)

Limit of this finding: Pools all intermittent fasting types.

Compared to regular dietary advice, intermittent fasting may result in little to no difference in weight loss or quality of life.

Where the evidence is mixed

In a 12-month trial in a racially diverse group, noon-to-8 pm eating without calorie counting produced more weight loss than a control group but not more than 25% daily calorie restriction. (Source 11)

  • Randomized trial, Certainty not rated.
  • Size: 90 adults randomised; 77 completers.
  • Who: adults with obesity in Chicago (about 33% Black, 46% Hispanic)
  • How long: 12 months.
  • Result: TRE vs control -4.61 kg (95% CI -7.37 to -1.85); calorie restriction vs control -5.42 kg (95% CI -9.13 to -1.71); TRE vs calorie restriction 0.81 kg (95% CI -3.07 to 4.69; P = 0.68)
  • Funding: independent: National Institutes of Health / NIDDK.

Time-restricted eating is more effective in producing weight loss when compared with control but not more effective than CR in a racially diverse population.

A meta-analysis of 20 randomised trials found time-restricted eating reduced weight versus no restriction, but adding it to energy restriction gave no additional weight-loss benefit. (Source 5)

  • Meta-analysis, Certainty not rated.
  • Size: 1,242 participants in 20 RCTs.
  • Who: adults.
  • How long: varied.
  • Result: TRE vs no restriction WMD -1.59 kg (95% CI -2.02 to -1.15); TRE+ER vs ER WMD -0.94 kg (95% CI -1.58 to -0.31)
  • Funding: not stated.

Limit of this finding: The authors' conclusion of no additional benefit sits alongside a small pooled difference for TRE+ER; windows of different lengths are pooled.

TRE independently promotes weight loss in adults, and combining of TRE with ER has no additional beneficial effects on weight loss.

A network meta-analysis of 47 trials found time-restricted eating reduced weight, but regimens tended to give modest loss at 1 to 3 months followed by regain by 4 to 6 months. (Source 12)

  • Meta-analysis, Certainty not rated.
  • Size: 3,363 participants in 47 RCTs.
  • Who: adults.
  • How long: varied.
  • Result: TRE MD -2.25 kg (95% CI -2.92 to -1.59); ADF MD -3.42 kg (95% CI -4.28 to -2.55); the abstract sentence does not state the comparator for these network mean differences.
  • Funding: not stated.

Each regimen likely leads to modest weight loss after 1–3 months, followed by weight regain by 4–6 months.

Where the research disagrees

Whether eating within 8 hours a day is linked to higher cardiovascular death

  • American Heart Association news release on an EPI|Lifestyle 2024 conference abstract (Zhong and colleagues), cohort: In NHANES survey data, eating in less than 8 hours a day was associated with a 91% higher risk of cardiovascular death and no lower risk of death overall. (Source 7)
  • Letter signed by 34 fasting and circadian researchers, 21 March 2024, position: The data were not peer reviewed, eating patterns were based on two days of recall, the under-8-hour group was only 2% of the sample, and smoking or illness could explain the association. (Source 13)
  • Randomised trial of 8-hour eating in type 2 diabetes (Pavlou 2023), rct: Over 6 months no serious adverse events were reported, though a trial of 75 people cannot measure cardiovascular deaths. (Source 8)

A common belief, and what the research shows

The belief: 16:8 burns more fat than a normal diet with the same calories.

What the research shows: In 12-month trials an 8-hour window was not better than ordinary daily calorie restriction, and a meta-analysis found adding it to calorie restriction gave no extra weight loss; some lean mass was lost.

References

  1. Diabetology & Metabolic Syndrome. Effects of time-restricted eating on people with type 2 diabetes: a systematic review and meta-analysis. 2026. DOI 10.1186/s13098-026-02138-8. Read the source
  2. JAMA Internal Medicine. 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. 2020. PMID 32986097, DOI 10.1001/jamainternmed.2020.4153. Read the source
  3. Cochrane (news release). Evidence behind intermittent fasting for weight loss fails to match hype. 2026. Read the source
  4. EurekAlert! / American Heart Association. 8-hour time-restricted eating linked to a 91% higher risk of cardiovascular death (EurekAlert copy of the AHA news release). 2024. Read the source
  5. International Journal of Behavioral Nutrition and Physical Activity. Efficiency of time-restricted eating and energy restriction on anthropometrics and body composition in adults: a systematic review and meta-analysis of randomized controlled trials. 2025. PMID 41034862, DOI 10.1186/s12966-025-01812-w. Read the source
  6. BMJ. Intermittent fasting strategies and their effects on body weight and other cardiometabolic risk factors: systematic review and network meta-analysis of randomised clinical trials. 2025. PMID 40533200, DOI 10.1136/bmj-2024-082007. Read the source
  7. American Heart Association Newsroom. 8-hour time-restricted eating linked to a 91% higher risk of cardiovascular death (news release on EPI|Lifestyle 2024 Abstract P192, not peer reviewed). 2024. Read the source
  8. JAMA Network Open. Effect of Time-Restricted Eating on Weight Loss in Adults With Type 2 Diabetes: A Randomized Clinical Trial. 2023. PMID 37889487, DOI 10.1001/jamanetworkopen.2023.39337. Read the source
  9. New England Journal of Medicine. Calorie Restriction with or without Time-Restricted Eating in Weight Loss. 2022. PMID 35443107, DOI 10.1056/NEJMoa2114833. Read the source
  10. Cochrane Database of Systematic Reviews. Intermittent fasting for adults with overweight or obesity. 2026. PMID 41692034, DOI 10.1002/14651858.CD015610.pub2. Read the source
  11. Annals of Internal Medicine. Time-Restricted Eating Without Calorie Counting for Weight Loss in a Racially Diverse Population: A Randomized Controlled Trial. 2023. PMID 37364268, DOI 10.7326/M23-0052. Read the source
  12. International Journal of Behavioral Nutrition and Physical Activity. Comparing caloric restriction regimens for effective weight management in adults: a systematic review and network meta-analysis. 2024. DOI 10.1186/s12966-024-01657-9. Read the source
  13. University of Illinois Chicago (hosted PDF). Collective response to the American Heart Association press release on time-restricted eating (letter signed by 34 researchers, 21 March 2024). 2024. Read the source
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