Study analysis · Nutrition and Healthy Aging · 2018
Eating in an 8-hour window dropped weight and blood pressure—without calorie counting. But there's a catch.
In a small 12-week study, obese adults who ate only between 10am and 6pm lost about 2.6% of their starting weight and lowered systolic blood pressure by about 7 mm Hg compared with people who didn't change their eating, but the study wasn't randomized so it can't prove cause and effect.
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 compared a group of people who tried time-restricted eating to a group from an older study who didn't. Because the groups weren't randomly assigned, we can't be sure the eating plan caused the weight loss—it might be other differences. It's a clue, not proof.
What’s the bottom line?
In a small 12-week study, obese adults who ate only between 10am and 6pm lost about 2.6% of their starting weight compared with people who didn't change their eating. They ate about 341 fewer calories per day without counting calories. Their systolic blood pressure dropped about 7 mm Hg. Other health markers didn't clearly change. The study wasn't randomized and used past controls, so results are preliminary.
How strong is this study?
The study is small and used an old control group, so it's not very strong. The results are interesting but need to be confirmed by bigger, randomized studies where people are assigned to groups by chance.
40 / 100
- COI disclosure+40/40
- Data availabilitydata not shared
- Code availabilitycode not shared
36 / 100
- Randomizationnot randomized
- Blindingblinding unclear
- Control group+15/15
- Sample size (n=46)+4.1/20
- Follow-up+10/10
100 / 100
77 / 100
- P-values+15/15
- Effect size+20/20
- 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
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. Non-randomized design with historical control group; no randomization; potential confounding; temporal changes; self-reported adherence; small pilot sample; cannot establish cause-effect.
COI Unknown
Could not determine conflict of interest status
No conflicts of interest or funding statement is present in the provided text, so the study's COI status cannot be determined.
The provided excerpt lacks author list, affiliations, conflict of interest declaration, and funding statement. Therefore, no COI assessment can be made. The study uses a historical control group from a previous trial by the same research group, which may introduce methodological bias but is not a disclosed conflict of interest.
Key takeaways
- 01
Weight: about 2.6% of initial body weight lost vs controls (absolute; kg not reported).
- 02
Energy intake: about 341 kcal/day lower (absolute).
- 03
Systolic blood pressure: about 7 mm Hg lower (absolute).
- 04
No significant differences for fat mass, lean mass, visceral fat, diastolic BP, LDL, HDL, triglycerides, fasting glucose, insulin, HOMA-IR, or homocysteine.
- 05
Adherence: 5.6 days/week.
- 06
Dropout: 26%.
- 07
For a 100 kg person, 2.6% weight loss is about 2.6 kg (about 5.7 lb) over 12 weeks, but the study did not report kg.
- 08
A 7 mm Hg systolic BP drop is clinically meaningful (e.g., 130 to 123 mm Hg).
- 09
Because controls were historical and not randomized, these are associations, not proof of cause and effect.
- 10
The study did not report absolute risk reductions for diseases.
Surprising findings
- Weight loss occurred without significant fat mass or visceral fat loss.Most people assume weight loss equals fat loss, but DXA showed no significant differential changes in fat mass, lean mass, or visceral fat versus controls.
- Systolic blood pressure improved, but nearly every other metabolic marker did not.Intermittent fasting is often promoted for broad metabolic benefits, yet here only systolic BP significantly changed. LDL, HDL, triglycerides, glucose, insulin, and HOMA-IR were unchanged.
- Adherence was high, but dropout was 26%.Participants reported following the eating window about 5.6 days/week, yet one in four dropped out. None said the diet itself made them quit, suggesting other barriers to sustainability.
- Self-reported baseline eating duration was only 11 hours, which the authors say is likely inaccurate.Objective studies show many adults eat over 15 hours a day, so self-reported food timing may be unreliable—a major caveat for time-restricted feeding research.
Practical takeaways
If you want a simple eating structure, an 8-hour window (e.g., 10am–6pm) may help you eat less without counting calories—expect modest weight loss of about 2.6% over 12 weeks and possibly a small blood pressure drop.
This was a small, non-randomized pilot with historical controls; it cannot prove cause and effect. The weight loss in kg was not reported, and participants were metabolically healthy obese adults.
low-to-medium confidenceDon't expect time-restricted feeding alone to fix cholesterol, blood sugar, or insulin resistance based on this study—those markers did not significantly improve.
Participants were metabolically healthy at baseline, and the study lasted only 12 weeks. Longer trials in less healthy populations are needed.
low confidenceIf you try an 8-hour window, track your blood pressure and weight, and talk to your doctor—especially if you take medications or have diabetes or heart disease.
The study excluded people with diabetes, cardiovascular disease, and those on weight-loss, lipid- or glucose-lowering medications.
low confidenceFocus on overall diet quality, not just timing. The study allowed ad libitum eating of any foods within the window, and long-term effects on food choices are unknown.
Dietary intake was self-reported and may be inaccurate; the study did not track food quality in detail.
low confidenceWhy this study matters
8-hour window, no calorie counting
23 obese adults ate ad libitum only between 10:00 and 18:00 and water-fasted from 18:00 to 10:00 for 12 weeks. They ate about 341 kcal/day less than matched historical controls and lost about 2.6% of initial body weight (absolute; kg not reported). Adherence averaged 5.6 days/week.
It offers a simple rule—eat within an 8-hour window—without tracking every bite. For people tired of calorie counting, that's appealing.
Blood pressure bonus, but not much else
Systolic blood pressure fell by about 7 mm Hg (absolute) versus controls. But fat mass, lean mass, visceral fat, diastolic BP, LDL, HDL, triglycerides, fasting glucose, insulin, HOMA-IR, and homocysteine did not significantly differ.
A 7 mm Hg systolic drop is clinically meaningful, yet most blood markers didn't budge. That makes people wonder: is it the timing or just eating fewer calories?
The fine print: non-randomized historical controls
This was a pilot study, not an RCT. The 23 intervention participants were compared with 23 matched historical controls from a previous trial conducted 2011–2015. Total n=46, dropout was 26%, and participants were metabolically healthy obese adults.
Headlines often say 'intermittent fasting works,' but this study can't prove cause and effect. The control group wasn't enrolled at the same time.
Weight loss without clear fat loss
Despite about 2.6% weight loss, DXA showed no significant changes in fat mass, lean mass, or visceral fat compared with controls. The study authors note no group×time interaction for these body composition measures.
People assume weight loss means fat loss. Here, the scale moved but body composition didn't clearly change—at least not detectably in this small, short study.
High adherence, high dropout paradox
Participants followed the 8-hour window on 5.6 days/week, yet 26% dropped out (6 of 23). None of the dropouts reported leaving because of diet issues.
If it's so easy, why did 1 in 4 quit? This hints that adherence in real life may be harder than a simple rule suggests.
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
In a small 12-week study, obese adults who ate only between 10am and 6pm lost about 2.6% of their starting weight compared with people who didn't change their eating. They ate about 341 fewer calories per day without counting calories. Their systolic blood pressure dropped about 7 mm Hg. Other health markers didn't clearly change. The study wasn't randomized and used past controls, so results are preliminary.
Research results
Weight: about 2.6% of initial body weight lost vs controls (absolute; kg not reported). Energy intake: about 341 kcal/day lower (absolute). Systolic blood pressure: about 7 mm Hg lower (absolute). No significant differences for fat mass, lean mass, visceral fat, diastolic BP, LDL, HDL, triglycerides, fasting glucose, insulin, HOMA-IR, or homocysteine. Adherence: 5.6 days/week. Dropout: 26%.
What this means - more context
For a 100 kg person, 2.6% weight loss is about 2.6 kg (about 5.7 lb) over 12 weeks, but the study did not report kg. A 7 mm Hg systolic BP drop is clinically meaningful (e.g., 130 to 123 mm Hg). Because controls were historical and not randomized, these are associations, not proof of cause and effect. The study did not report absolute risk reductions for diseases.
To investigate whether 8-hour time-restricted feeding reduces body weight and improves metabolic disease risk factors in obese adults.
In this 12-week non-randomized pilot, 23 obese adults ate ad libitum only between 10:00 and 18:00 and were compared with 23 matched historical controls. Body weight decreased by 2.6% of initial body weight (absolute; kg not reported) and daily energy intake decreased by 341 kcal/day (absolute) relative to controls. Systolic blood pressure fell by 7 mm Hg (absolute). Fat mass, lean mass, visceral fat, diastolic blood pressure, lipids, glucose, insulin, HOMA-IR, and homocysteine did not significantly differ. Adherence averaged 5.6 days/week; dropout was 26%.
Methods Used
Non-randomized 12-week pilot intervention. Obese adults (n=23) prescribed 8-h time-restricted feeding (ad libitum 10:00–18:00, water fast 18:00–10:00) vs matched historical no-intervention controls (n=23) from a prior trial. Outcomes: body weight (primary), DXA body composition, blood pressure, fasting lipids/glucose/insulin/HOMA-IR/homocysteine, 7-day food records, pedometer steps. Intention-to-treat with last observation carried forward.
Main Finding
8-h time-restricted feeding produced modest weight loss of about 2.6% of initial body weight over 12 weeks (absolute change; kg not reported) versus controls, plus absolute reductions of about 341 kcal/day in energy intake and about 7 mm Hg in systolic blood pressure. No significant improvements in fat mass, lean mass, visceral fat, diastolic BP, LDL, HDL, triglycerides, fasting glucose, fasting insulin, HOMA-IR, or homocysteine.
Confidence Level
Low to moderate. Non-randomized historical control, small pilot (n=46 total), short 12 weeks, self-reported adherence and diet, 26% dropout, no kg weight loss reported, and metabolically healthy obese participants limit generalizability. Not retracted; no corrections reported.
Study Flags
Red Flags
- •Non-randomized historical control group; not a randomized controlled trial
- •Small pilot (n=46 total), short 12-week duration, 26% dropout
- •Adherence and dietary intake self-reported; weight loss in kg not reported
- •Participants were metabolically healthy obese adults, limiting generalizability
Surprising Findings
Weight loss occurred without significant fat mass or visceral fat loss.
Most people assume weight loss equals fat loss, but DXA showed no significant differential changes in fat mass, lean mass, or visceral fat versus controls.
Practical Takeaways
If you want a simple eating structure, an 8-hour window (e.g., 10am–6pm) may help you eat less without counting calories—expect modest weight loss of about 2.6% over 12 weeks and possibly a small blood pressure drop.
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
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.
Human Cohort Study
Subject
Moderate probability
on the GRADE evidence scale
This study compared a group of people who tried time-restricted eating to a group from an older study who didn't. Because the groups weren't randomly assigned, we can't be sure the eating plan caused the weight loss—it might be other differences. It's a clue, not proof.
Strengths
- Prospective intervention with matched control group
- Matching on age, BMI, and sex
- Use of DXA for body composition
Weaknesses
- Non-randomized design
- Historical control group (not concurrent)
- Small sample size (pilot)
Methodology
Evidence Keywords
Statistical Reporting
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
In a small 12-week study, obese adults who ate only between 10am and 6pm lost about 2.6% of their starting weight compared with people who didn't change their eating. They ate about 341 fewer calories per day without counting calories. Their systolic blood pressure dropped about 7 mm Hg. Other health markers didn't clearly change. The study wasn't randomized and used past controls, so results are preliminary.
Research results
Weight: about 2.6% of initial body weight lost vs controls (absolute; kg not reported). Energy intake: about 341 kcal/day lower (absolute). Systolic blood pressure: about 7 mm Hg lower (absolute). No significant differences for fat mass, lean mass, visceral fat, diastolic BP, LDL, HDL, triglycerides, fasting glucose, insulin, HOMA-IR, or homocysteine. Adherence: 5.6 days/week. Dropout: 26%.
What this means - more context
For a 100 kg person, 2.6% weight loss is about 2.6 kg (about 5.7 lb) over 12 weeks, but the study did not report kg. A 7 mm Hg systolic BP drop is clinically meaningful (e.g., 130 to 123 mm Hg). Because controls were historical and not randomized, these are associations, not proof of cause and effect. The study did not report absolute risk reductions for diseases.
To investigate whether 8-hour time-restricted feeding reduces body weight and improves metabolic disease risk factors in obese adults.
In this 12-week non-randomized pilot, 23 obese adults ate ad libitum only between 10:00 and 18:00 and were compared with 23 matched historical controls. Body weight decreased by 2.6% of initial body weight (absolute; kg not reported) and daily energy intake decreased by 341 kcal/day (absolute) relative to controls. Systolic blood pressure fell by 7 mm Hg (absolute). Fat mass, lean mass, visceral fat, diastolic blood pressure, lipids, glucose, insulin, HOMA-IR, and homocysteine did not significantly differ. Adherence averaged 5.6 days/week; dropout was 26%.
Methods Used
Non-randomized 12-week pilot intervention. Obese adults (n=23) prescribed 8-h time-restricted feeding (ad libitum 10:00–18:00, water fast 18:00–10:00) vs matched historical no-intervention controls (n=23) from a prior trial. Outcomes: body weight (primary), DXA body composition, blood pressure, fasting lipids/glucose/insulin/HOMA-IR/homocysteine, 7-day food records, pedometer steps. Intention-to-treat with last observation carried forward.
Main Finding
8-h time-restricted feeding produced modest weight loss of about 2.6% of initial body weight over 12 weeks (absolute change; kg not reported) versus controls, plus absolute reductions of about 341 kcal/day in energy intake and about 7 mm Hg in systolic blood pressure. No significant improvements in fat mass, lean mass, visceral fat, diastolic BP, LDL, HDL, triglycerides, fasting glucose, fasting insulin, HOMA-IR, or homocysteine.
Confidence Level
Low to moderate. Non-randomized historical control, small pilot (n=46 total), short 12 weeks, self-reported adherence and diet, 26% dropout, no kg weight loss reported, and metabolically healthy obese participants limit generalizability. Not retracted; no corrections reported.
Study Flags
Red Flags
- •Non-randomized historical control group; not a randomized controlled trial
- •Small pilot (n=46 total), short 12-week duration, 26% dropout
- •Adherence and dietary intake self-reported; weight loss in kg not reported
- •Participants were metabolically healthy obese adults, limiting generalizability
Surprising Findings
Weight loss occurred without significant fat mass or visceral fat loss.
Most people assume weight loss equals fat loss, but DXA showed no significant differential changes in fat mass, lean mass, or visceral fat versus controls.
Practical Takeaways
If you want a simple eating structure, an 8-hour window (e.g., 10am–6pm) may help you eat less without counting calories—expect modest weight loss of about 2.6% over 12 weeks and possibly a small blood pressure drop.
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
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.
Human Cohort Study
Subject
Moderate probability
on the GRADE evidence scale
This study compared a group of people who tried time-restricted eating to a group from an older study who didn't. Because the groups weren't randomly assigned, we can't be sure the eating plan caused the weight loss—it might be other differences. It's a clue, not proof.
Strengths
- Prospective intervention with matched control group
- Matching on age, BMI, and sex
- Use of DXA for body composition
Weaknesses
- Non-randomized design
- Historical control group (not concurrent)
- Small sample size (pilot)
Methodology
Evidence Keywords
Statistical Reporting
Scoring
How strong is this study?
The study is small and used an old control group, so it's not very strong. The results are interesting but need to be confirmed by bigger, randomized studies where people are assigned to groups by chance.
40 / 100
- COI disclosure+40/40
- Data availabilitydata not shared
- Code availabilitycode not shared
36 / 100
- Randomizationnot randomized
- Blindingblinding unclear
- Control group+15/15
- Sample size (n=46)+4.1/20
- Follow-up+10/10
100 / 100
77 / 100
- P-values+15/15
- Effect size+20/20
- 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
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. Non-randomized design with historical control group; no randomization; potential confounding; temporal changes; self-reported adherence; small pilot sample; cannot establish cause-effect.
COI Unknown
Could not determine conflict of interest status
No conflicts of interest or funding statement is present in the provided text, so the study's COI status cannot be determined.
The provided excerpt lacks author list, affiliations, conflict of interest declaration, and funding statement. Therefore, no COI assessment can be made. The study uses a historical control group from a previous trial by the same research group, which may introduce methodological bias but is not a disclosed conflict of interest.
Standing
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1 video from Thomas DeLauer cite this study, drawing 1 claim from it.
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Evidence contradicts this claim.
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Authored by
8 researchersIf this is your work, this is how we attribute it on Fit Body Science. Kelsey Gabel is listed as the lead author.