The Study
The effects of graded levels of calorie restriction: VIII. Impact of short term calorie and protein restriction on basal metabolic rate in the C57BL/6 mouse
This study didn't prove that eating less food slows down a mouse's metabolism. Instead, it showed that when mice lose weight, their bodies change shape — like losing fat or shrinking organs — and that's enough to explain why they burn less energy. It's like thinking a car uses less gas because the engine is slower, but really it's just because the car is lighter.
Analysis score
Maximum 72 for a cohort study.
Where the score came from
When mice eat less, they get smaller — especially in organs like the liver and tail. This makes them burn less energy, not because their cells slow down, but because they have less tissue to power.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 517 / 100
Quality score
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.
Key takeaways
Summary
Based on the study abstract and findings.
- 1This suggests that in humans, weight loss may lower metabolism not because the body 'slows down' metabolically, but simply because we lose weight and organs — meaning metabolic slowdown may be a physical consequence, not a biological defense.
- 2Mice on 40% calorie restriction had 56% lower BMR than normal mice — but this drop was fully predicted by how much their liver, spleen, pancreas, tail, and fat tissue shrank.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Oncotarget
Year
2017
Authors
S. Mitchell, Zhanhui Tang, Celine Kerbois, Camille Delville, Davina Derous, Cara L. Green, Yingchun Wang, J. J. Han, Luonan Chen, A. Douglas, D. Lusseau, D. Promislow, J. Speakman
Related Content
Claims (7)
When a person consumes significantly fewer calories over an extended period, their body produces higher levels of hunger-related signals and lowers its resting energy expenditure.
About 70% of the energy the body uses each day comes from basic life-sustaining processes, and significantly reducing calorie intake triggers biological changes that increase the likelihood of regaining lost weight.
In C57BL/6 mice, reducing calorie intake lowers basal metabolic rate in proportion to how much food is cut, and this drop is entirely explained by the loss of mass in the liver, spleen, pancreas, tail, and brown fat; however, reducing protein intake without changing total calories does not lower basal metabolic rate.
When scientists adjust metabolic rate measurements in mice on calorie-restricted diets using standard body size ratios, the results falsely suggest metabolism slows down because the adjustments do not reflect how different tissues shrink at different rates.
During calorie restriction in mice, changes in body composition account for the drop in metabolic rate and body temperature, and these effects are not due to a separate reduction in metabolic function when organ-specific models are applied.
Basal metabolic rate predictions in mice using only total body weight or body composition categories like lean or fat mass are too high during calorie restriction; including measurements of individual organs such as the liver, spleen, and tail improves prediction accuracy.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.