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Study analysis · Current developments in nutrition · 2019

8-hour eating window: weight loss without a metabolic crash or eating-disorder red flags? A small 12-week study says maybe—but the fine print matters.

In 23 adults with obesity, eating only between 10am and 6pm for 12 weeks was linked to a 2.6% relative weight loss, with no significant changes in metabolism, eating behaviors, or blood counts—but there was no control group and absolute pounds lost weren't reported.

Reading level
Very low certainty
Level 2b · Individual cohort studyAssociation, not causationNo causal claims

Overview

What the study found

The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.

In simple terms

This study gave 23 people with obesity a special eating schedule for 12 weeks and watched what happened. It can tell us that in this small group, they lost some weight and didn't have big changes in some health measures. But because there was no comparison group, we can't say for sure that the eating schedule caused the weight loss or that it's safe for everyone.

What’s the bottom line?

Researchers asked 23 adults with obesity to eat only between 10am and 6pm for 12 weeks. They checked weight, metabolism, eating behaviors, blood counts, and side effects.

How strong is this study?

The study is small and didn't compare the diet to another group, so it's hard to know if the changes were really due to the diet or something else. Also, we only have a short summary of the study, not all the details, so we can't be very confident in the results.

Reporting

0 / 100

  • COI disclosureconflicts of interest not disclosed
  • Data availabilitydata not shared
  • Code availabilitycode not shared
Methodology

15 / 100

  • Randomizationnot randomized
  • Blindingblinding unclear
  • Control groupno control group
  • Sample size (n=23)+2.2/20
  • Follow-up+10/10
Publication

100 / 100

Statistical

23 / 100

  • P-values+15/15
  • Effect sizeno effect size reported
  • Confidence intervalsno confidence intervals
  • Pre-registrationnot pre-registered

Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.

Where it sits

RCT reviews

Max 100

Randomized Trials

Max 90

Reviews of Cohort Studies

Max 85

Cohort Studies

Max 72

Reviews of Case-Control Studies

Max 63

Case-Control Studies

Max 58

Cross-Sectional & Case Series

Max 50

Expert Opinion

Max 5
StrongerWeaker
Cohort Studies
Level 2b
31

31 / 100

Probability of being correct

Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.

This design cannot establish causation — the findings describe an association, not a cause. Single-arm, uncontrolled pre-post design cannot establish causation. Without a control group, changes could be due to time, regression to the mean, placebo effect, or other confounders. No randomization or blinding.

No Conflicts

No conflicts of interest identified

Not Disclosed

No conflicts identified. Study funded by university pilot grant and NIH training grant; no industry involvement or author COI disclosed.

Funder Involved
Undisclosed — Suspicious

Funders

University of Illinois Chicago Campus Research Board Pilot Grant
NIH T32HL007909

Conflict Details

Not specified
Funding

University of Illinois Chicago Campus Research Board Pilot Grant: Funding source

Not specified
Funding

NIH T32HL007909: Funding source

No conflict of interest or competing interests section was present in the provided text. Funding is from academic and government sources, not industry. Author affiliations were not provided, so employment relationships with funders cannot be fully assessed.

Key takeaways

  1. 01

    Body weight decreased by 2.6% relative from baseline (absolute kg not reported).

  2. 02

    Resting metabolic rate did not significantly change (baseline 1431 ± 62 kcal/day; week 12 1318 ± 61 kcal/day).

  3. 03

    No significant changes in self-reported GI or neurological side effects, eating disorder symptoms, body image concerns, or complete blood count parameters.

  4. 04

    The 2.6% relative weight loss is small; absolute weight change in kg was not reported in the abstract.

  5. 05

    Because there was no control group and only 23 people, we cannot know how much weight they would have lost without the diet.

  6. 06

    The study found no sign of harm to metabolism or eating behaviors over 12 weeks, but absolute risk/benefit is not calculable from the abstract.

Practical takeaways

If you are considering an 8-hour time-restricted feeding window (10am–6pm), this small 12-week study found no significant worsening of eating disorder symptoms, body image concerns, resting metabolic rate, or complete blood count in adults with obesity. Discuss with a healthcare provider before starting, especially if you have a history of disordered eating.

This was a single-arm study of 23 adults with obesity, with no control group, no randomization, and only 12 weeks of follow-up. Absolute weight change was not reported, and the full methodology is unavailable. The findings do not prove long-term safety or effectiveness.

low confidence

Don't assume that 8-hour TRF will crash your metabolism. In this study, resting metabolic rate did not significantly change from baseline to week 12 (1431 ± 62 kcal/day to 1318 ± 61 kcal/day), though the numerical decrease was not statistically significant.

The sample was small (n=23), there was no control group, and the numerical drop in RMR could still be clinically meaningful. The abstract does not report confidence intervals or effect sizes, so the precision of this estimate is unknown.

low confidence

Why this study matters

Small relative weight loss, absolute pounds unknown

Body weight decreased by 2.6 ± 0.5% relative from baseline after 12 weeks of 8-hour time-restricted feeding (P < 0.001). The abstract does not report absolute weight change in kilograms, so we don't know how many pounds that represents per person. There was no control group, so we cannot say how much weight they would have lost without TRF.

Most people want to know 'how much weight will I lose?' A 2.6% relative drop is small and hard to translate without absolute numbers. The lack of a control group means the weight loss could be partly due to other factors like season, attention, or spontaneous changes.

Metabolism didn't significantly change—but numbers drifted down

Resting metabolic rate was 1431 ± 62 kcal/day at baseline and 1318 ± 61 kcal/day at week 12. The abstract states RMR 'did not change over time,' meaning no statistically significant change. However, the numerical drop of about 113 kcal/day may still matter, and the study was small and short.

A common fear is that fasting slows metabolism. This study offers some reassurance that RMR didn't significantly drop over 12 weeks, but the numerical decrease means we can't rule out a real effect that the small sample couldn't detect.

No significant worsening of eating disorder symptoms or body image

The study measured eating disorder symptoms including depression, binge eating, purgative behavior, fear of fatness, restrictive eating, and avoidance of forbidden foods. It also measured body size and shape concerns, cognitive restraint, uncontrolled eating, and emotional eating. None changed significantly from baseline to week 12.

A major criticism of intermittent fasting is that it might trigger disordered eating or obsession with food. This small study found no significant short-term worsening, which is reassuring—but it was not a randomized controlled trial and relied on self-report.

Blood counts and adverse events stayed stable

There were no significant changes in any complete blood count parameters from baseline to week 12. Self-reported gastrointestinal or neurological adverse events also did not change over time.

Safety is more than weight loss. This study checked basic health markers and side effects, finding no significant short-term harms. But self-reported side effects can be underreported, and the study was only 12 weeks.

Authors conclude TRF is 'safe'—but the study design limits that claim

The authors state: 'This study is the first to show that TRF is a safe diet therapy for weight loss as it does not negatively impact eating disorder symptoms, eating behaviors, resting metabolic rate, or measures of overall health, such as complete blood count.' However, the study was a single-arm pre-post intervention with n=23, no control group, no blinding or randomization mentioned, and only 12 weeks of follow-up.

The word 'safe' is powerful. Viewers should understand that safety conclusions from a small, uncontrolled, short study are preliminary. The abstract itself notes no effect sizes or confidence intervals, and the full methodology is unavailable.

Want the whole report?

Detailed mode opens the full scientific breakdown — every score component, the methodology, conflicts of interest, the evidence analysis behind each claim, and the raw study data.

Standing

Who’s using this study?

The videos and claims on this site that lean on this study, and the researchers who wrote it.

1 video from Thomas DeLauer cite this study, drawing 1 claim from it.

Thomas DeLauer
Try This Today to Stop Insulin Resistance COLD in its Tracks (no dieting required)
Citing claim
Supports
All 1 video reference this study through extracted claims.

Authored by

2 researchers

If this is your work, this is how we attribute it on Fit Body Science. Kelsey Gabel is listed as the lead author.