Randomised controlled trialindependent cross-checkabstract checked★ key study I-INS-118 in-depth review
Low-carbohydrate diets and calories burned after weight loss
Effects of a low carbohydrate diet on energy expenditure during weight loss maintenance: randomized trial.
Overview
Ebbeling CB et al.. BMJ 2018 · PMID 30429127 · DOI 10.1136/bmj.k4583
People on a low-carbohydrate diet burned about 200 more calories per day than on a high-carbohydrate diet while keeping weight off.
Does the study support the specific claim? Partly · Methodological quality: moderate
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Test diet carbohydrate and energy expenditure.
- How was the study done?
Randomised trial over 20 weeks.
- How many people, animals or samples were studied?
164 adults after weight loss.
- What was actually found?
Low-carb: +209 kcal/d.
- How large was the observed effect?
52 kcal/d per 10% less carbohydrate.
- What do the results mean in everyday life?
Insulin may play some role in weight regulation.
- What are the study's limitations?
Results debated; correction published.
- What does it say about Elawady's specific claim?
Partly supports a role of insulin, not 'only cause'.
- Do the results apply to Germany and Europe?
Applicable.
- What can explicitly not be concluded from this study?
Cannot show insulin is the only cause.
Scientific in-depth review
1. Full reference
- Authors
- Ebbeling CB et al.
- Journal
- BMJ
- Year
- 2018
- Identifier
- PMID 30429127 DOI 10.1136/bmj.k4583
- Verification
- verified – PubMed efetch 2026-10-26; Crossref 2026-10-26
- Retracted
- no
- Corrections
ErratumIn BMJ 2020;371:m4264 (correction notice; not a retraction)
- Extent checked
- abstract only
- Conflicts of interest and funding
Research support declared; no relevant financial relationships (record).
2. Research question
Do diets varying in carbohydrate affect total energy expenditure during weight-loss maintenance?
3. Study design and population
- Study design
- Randomised controlled trial – Randomised trial (3 diets, 20 weeks) after 12% weight loss
- Population
Adults with BMI >=25
- Country
USA (2 sites)
- Period
2014-2017
- Sample size
164
- Inclusion and exclusion criteria
18-65 years, BMI >=25, achieved 12% weight loss
4. Methods and endpoints
- Exposure / intervention
Low (20%) or moderate (40%) carbohydrate diet
- Comparator
High (60%) carbohydrate diet
- Endpoints
Total energy expenditure (doubly labelled water)
- Statistical methods
ITT and per-protocol; trend per 10% carbohydrate
5. Actual results
- Results
Energy expenditure increased by 52 kcal/d (23-82) per 10% decrease in carbohydrate; low vs high carbohydrate +209 kcal/d (91-326) ITT, +278 (144-411) per protocol; among highest insulin secretors +308 kcal/d (ITT).
- Absolute risks
not reported
- Authors' conclusion
Consistent with the carbohydrate-insulin model, lowering carbohydrate increased energy expenditure during weight-loss maintenance.
6. Strengths
- Randomised
- Doubly labelled water
7. Weaknesses
- Post-hoc debates about exclusions and measurement
- Weight-maintenance phase only
- Did not measure fat mass as primary outcome
8. Risk of bias
- Orienting tool
- RoB 2
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- some concerns
- Rationale
Analysis choices debated in the literature; correction published.
9. Assessment of the statistical interpretation
CIs log-symmetric not applicable (differences); effect modification by insulin secretion supports a role of insulin but not exclusivity.
10. Relevance to the specific claim
Supports that insulin-related diet composition can affect energy expenditure (partial support for a role of insulin), but does not show insulin is the only cause of obesity.
11. Independent contrary findings
12. Transferability to Germany and Europe
Directly applicable; same biology and clinical standards in Europe.
13. Overall methodological judgement
Best supporting evidence for the carbohydrate-insulin model; contested and not exclusive.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | moderate |
| Directness | direct |
| Reproducibility | not replicated |
| Consistency with the overall evidence | mixed |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
15. Linked fact checks
- Insulin is the single and only cause of obesity (local or generalised) because it is the only hormone that builds fat and blocks fat breakdown (lipolysis). – Studies with mixed or unclear results
- Calories are not a relevant concept ('there is no such thing as calories'); his system is based on high calorie intake, and people lose weight while eating sugar, juices, fats, potatoes and rice, because with 'zero insulin' no fat is formed (the passage continues: 'even if you drink oil, even if you swallow bags of sugar'). Elsewhere he says he drinks 6 litres of sugar-cane juice and eats baladi ghee, rice and potatoes every day. – Studies with mixed or unclear results