Study analysis · Nutrients · 2024
This 4-week diet trend didn't make people lose weight—here's why your morning fast might be pointless.
Eating only between 7 am and 3 pm for a month didn't help young adults with overweight lose weight or get healthier—compared to eating whenever they wanted.
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 tried to see if eating only during the day helps people lose weight or get healthier, but it only tested 17 people for four weeks. It’s like testing a new snack on your friends and then saying it works for everyone — we just don’t have enough people or time to be sure.
What’s the bottom line?
Scientists tested if eating only between 7 am and 3 pm helps overweight young adults lose weight or get healthier, without eating less food.
How strong is this study?
The study did a good job by randomly assigning who ate when and making sure everyone did the same thing twice — that’s smart! But they didn’t hide which group people were in, and too many people dropped out, so we can’t fully trust the results.
40 / 100
- COI disclosure+40/40
- Data availabilitydata not shared
- Code availabilitycode not shared
58 / 100
- Randomization+20/20
- Blindingblinding unclear
- Control group+15/15
- Sample size (n=17)+1.6/20
- Follow-up+10/10
100 / 100
46 / 100
- P-values+15/15
- Effect sizeno effect size reported
- Confidence intervalsno confidence intervals
- Pre-registration+15/15
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 reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 560 / 100
Probability of being correct
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
This design can establish causation. Although this is a randomized controlled trial, the small sample size (n=17), short duration (4 weeks), and unclear blinding reduce confidence in causal inference. The crossover design helps control for individual variability, but lack of blinding introduces potential performance and assessment bias.
No Conflicts
No conflicts of interest identified
No conflicts of interest or funding sources were disclosed in the study text, and no industry ties or funder involvement were identified.
The study lacks a declared funding statement or conflict of interest section. While the methods mention use of commercial products (Simisure®, Kellogg’s®), there is no indication of industry funding, author affiliations with these companies, or funder influence on study design or analysis. The absence of disclosure raises transparency concerns but does not constitute evidence of conflict.
Key takeaways
- 01
People lost about 1 pound and their BMI dropped by 1 point on average — but only in women, and only when looking at their own changes before and after.
- 02
When compared to people eating normally, there was no real difference.
- 03
The tiny weight loss seen in women might just be normal day-to-day fluctuation — not a real effect of the eating schedule.
Surprising findings
- Women showed a statistically significant weight and BMI drop in before-after analysis (p=0.006 and p=0.009), but not in between-group comparison.Most people assume eTRE works best in women due to hormonal differences—but here, even their 'positive' result vanished when compared to the control group.
- Only one participant had elevated fasting glucose—most were metabolically healthy despite being overweight.The study population was 'metabolically healthy obese'—so even if eTRE works for people with prediabetes, it likely won't help those just carrying extra weight without metabolic dysfunction.
Practical takeaways
If you're trying eTRE to lose weight, track your calories—this study suggests timing alone won't cut it.
This study only tested young adults (mean age 25.8) with overweight—not older adults, diabetics, or those with metabolic disease.
medium confidenceDon't assume eTRE improves blood sugar or cholesterol unless you have prediabetes or insulin resistance.
The participants were mostly metabolically healthy—results may not apply to those with existing metabolic dysfunction.
medium confidenceIf you enjoy eTRE for routine or sleep reasons, keep doing it—but don't expect it to be a magic weight-loss tool.
No adverse effects were reported, so it's safe—but not necessarily effective for metabolic health in this group.
high confidenceWhy this study matters
No Weight Loss—Even in Women
Women lost an average of 1.0 kg and 1.0 BMI point in a before-after analysis, but this change wasn't statistically significant when compared to the control group eating freely. The study had only 17 participants, and the weight loss could have been random fluctuation.
Most people think time-restricted eating automatically leads to weight loss—this study shows it might not work at all, even in the group most likely to benefit.
No Metabolic Improvements
The study measured fasting glucose, insulin, cholesterol, triglycerides, blood pressure, and appetite—and found zero significant changes after 4 weeks of early time-restricted eating (7 am–3 pm).
People adopt eTRE hoping to fix blood sugar or cholesterol—this study says it doesn't work in young adults with overweight, even if they're otherwise healthy.
The 10-Person Subgroup Anomaly
In a subgroup of just 10 participants, blood glucose dropped slightly at the 15-minute mark during a meal test—but this wasn't replicated in the full group and had no lasting effect.
A tiny, fleeting blip in one small group got mentioned in the paper—but it didn't hold up under scrutiny. This is how misleading headlines get made.
They Didn't Even Track Calories
The study allowed participants to eat 'ad libitum'—meaning they could eat as much as they wanted during their 8-hour window—and didn't measure actual calorie intake.
If people ate fewer calories during eTRE, that could explain any weight loss—but since they didn't measure it, we don't know if the schedule or the calories caused any effect.
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.
Overview
What the study found
The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Scientists tested if eating only between 7 am and 3 pm helps overweight young adults lose weight or get healthier, without eating less food.
Research results
People lost about 1 pound and their BMI dropped by 1 point on average — but only in women, and only when looking at their own changes before and after. When compared to people eating normally, there was no real difference.
What this means - more context
The tiny weight loss seen in women might just be normal day-to-day fluctuation — not a real effect of the eating schedule.
This study evaluated whether early time-restricted eating (eTRE, 7:00 am–3:00 pm) improves metabolic and body composition outcomes in young adults with overweight or obesity.
In a 4-week randomized crossover trial with 17 participants, eTRE did not significantly improve fasting glucose, insulin, lipids, blood pressure, body weight, fat mass, waist/hip circumference, or appetite ratings compared to ad libitum eating. A within-group weight/BMI reduction in women was not significant in between-group analysis.
Methods Used
17 young adults (mean age 25.8, BMI 32.0) completed a randomized, crossover, controlled trial with 4 weeks of eTRE (16:8) and 4 weeks of ad libitum eating, separated by a 4-week washout. Outcomes included anthropometrics, fasting biochemistry, mixed-meal tolerance tests, and appetite ratings via VAS.
Main Finding
eTRE for 4 weeks did not significantly alter metabolic markers, body composition, or appetite in young adults with overweight or obesity; a non-significant 1.0 kg weight and 1.0 BMI reduction in women was observed but not sustained in between-group comparison.
Confidence Level
Moderate — randomized crossover design with control group and objective measures, but limited by small sample size (n=17), short duration, and lack of caloric intake monitoring.
Study Flags
Red Flags
- •Small sample size (n=17)
- •Short intervention duration (4 weeks)
- •No measurement of actual caloric intake
No biological mechanisms were identified in this study. This may be an epidemiological, observational, or survey-based study that reports associations rather than proposing causal biological pathways.
Surprising Findings
Women showed a statistically significant weight and BMI drop in before-after analysis (p=0.006 and p=0.009), but not in between-group comparison.
Most people assume eTRE works best in women due to hormonal differences—but here, even their 'positive' result vanished when compared to the control group.
Practical Takeaways
If you're trying eTRE to lose weight, track your calories—this study suggests timing alone won't cut it.
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 560 / 100
Probability of being correct
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Human RCT
Subject
Moderate probability
on the GRADE evidence scale
This study tried to see if eating only during the day helps people lose weight or get healthier, but it only tested 17 people for four weeks. It’s like testing a new snack on your friends and then saying it works for everyone — we just don’t have enough people or time to be sure.
No conflicts of interest were detected in this study. No score impact.
Strengths
- Randomized crossover design reduces individual variability by using each participant as their own control
- Clear intervention protocol with defined eating window and washout period
- Use of standardized meal tolerance test (MTT) to assess glycemic response
Weaknesses
- Very small sample size (n=17) with low statistical power
- Blinding status is unknown, risking performance and detection bias
- No measurement of actual caloric intake, so weight changes may reflect unmeasured dietary changes
Methodology
Evidence Keywords
Statistical Reporting
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Scientists tested if eating only between 7 am and 3 pm helps overweight young adults lose weight or get healthier, without eating less food.
Research results
People lost about 1 pound and their BMI dropped by 1 point on average — but only in women, and only when looking at their own changes before and after. When compared to people eating normally, there was no real difference.
What this means - more context
The tiny weight loss seen in women might just be normal day-to-day fluctuation — not a real effect of the eating schedule.
This study evaluated whether early time-restricted eating (eTRE, 7:00 am–3:00 pm) improves metabolic and body composition outcomes in young adults with overweight or obesity.
In a 4-week randomized crossover trial with 17 participants, eTRE did not significantly improve fasting glucose, insulin, lipids, blood pressure, body weight, fat mass, waist/hip circumference, or appetite ratings compared to ad libitum eating. A within-group weight/BMI reduction in women was not significant in between-group analysis.
Methods Used
17 young adults (mean age 25.8, BMI 32.0) completed a randomized, crossover, controlled trial with 4 weeks of eTRE (16:8) and 4 weeks of ad libitum eating, separated by a 4-week washout. Outcomes included anthropometrics, fasting biochemistry, mixed-meal tolerance tests, and appetite ratings via VAS.
Main Finding
eTRE for 4 weeks did not significantly alter metabolic markers, body composition, or appetite in young adults with overweight or obesity; a non-significant 1.0 kg weight and 1.0 BMI reduction in women was observed but not sustained in between-group comparison.
Confidence Level
Moderate — randomized crossover design with control group and objective measures, but limited by small sample size (n=17), short duration, and lack of caloric intake monitoring.
Study Flags
Red Flags
- •Small sample size (n=17)
- •Short intervention duration (4 weeks)
- •No measurement of actual caloric intake
No biological mechanisms were identified in this study. This may be an epidemiological, observational, or survey-based study that reports associations rather than proposing causal biological pathways.
Surprising Findings
Women showed a statistically significant weight and BMI drop in before-after analysis (p=0.006 and p=0.009), but not in between-group comparison.
Most people assume eTRE works best in women due to hormonal differences—but here, even their 'positive' result vanished when compared to the control group.
Practical Takeaways
If you're trying eTRE to lose weight, track your calories—this study suggests timing alone won't cut it.
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 560 / 100
Probability of being correct
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Human RCT
Subject
Moderate probability
on the GRADE evidence scale
This study tried to see if eating only during the day helps people lose weight or get healthier, but it only tested 17 people for four weeks. It’s like testing a new snack on your friends and then saying it works for everyone — we just don’t have enough people or time to be sure.
No conflicts of interest were detected in this study. No score impact.
Strengths
- Randomized crossover design reduces individual variability by using each participant as their own control
- Clear intervention protocol with defined eating window and washout period
- Use of standardized meal tolerance test (MTT) to assess glycemic response
Weaknesses
- Very small sample size (n=17) with low statistical power
- Blinding status is unknown, risking performance and detection bias
- No measurement of actual caloric intake, so weight changes may reflect unmeasured dietary changes
Methodology
Evidence Keywords
Statistical Reporting
Scoring
How strong is this study?
The study did a good job by randomly assigning who ate when and making sure everyone did the same thing twice — that’s smart! But they didn’t hide which group people were in, and too many people dropped out, so we can’t fully trust the results.
40 / 100
- COI disclosure+40/40
- Data availabilitydata not shared
- Code availabilitycode not shared
58 / 100
- Randomization+20/20
- Blindingblinding unclear
- Control group+15/15
- Sample size (n=17)+1.6/20
- Follow-up+10/10
100 / 100
46 / 100
- P-values+15/15
- Effect sizeno effect size reported
- Confidence intervalsno confidence intervals
- Pre-registration+15/15
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 reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 560 / 100
Probability of being correct
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
This design can establish causation. Although this is a randomized controlled trial, the small sample size (n=17), short duration (4 weeks), and unclear blinding reduce confidence in causal inference. The crossover design helps control for individual variability, but lack of blinding introduces potential performance and assessment bias.
No Conflicts
No conflicts of interest identified
No conflicts of interest or funding sources were disclosed in the study text, and no industry ties or funder involvement were identified.
The study lacks a declared funding statement or conflict of interest section. While the methods mention use of commercial products (Simisure®, Kellogg’s®), there is no indication of industry funding, author affiliations with these companies, or funder influence on study design or analysis. The absence of disclosure raises transparency concerns but does not constitute evidence of conflict.
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 Big Think Clips cite this study, drawing 1 claim from it.
- Very strong evidence
Randomized or controlled trials support this claim, alongside consistent supporting evidence.
Evidence
Authored by
11 researchersIf this is your work, this is how we attribute it on Fit Body Science. Dalila Rubí Mena-Hernández is listed as the lead author.