The Study
Effect of caloric restriction on organ size and its contribution to metabolic adaptation: an ancillary analysis of CALERIE 2
This study showed that when people ate less food for two years, their bodies lost weight and burned fewer calories than expected. It tried to figure out why by measuring organs, but it didn't prove that shrinking organs caused the slower metabolism—it just showed they happened together.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
When people eat much less for a long time, their bodies slow down burning calories more than expected — even after they stop losing weight.
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 569 / 100
Quality score
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes — this means dieting can make your body more efficient at saving energy, making it harder to keep losing weight or maintain weight loss.
- 2People ate 25% less for 2 years, lost 13% of their weight, and burned 13% more calories than expected based on their new body size.
- 3Their liver, heart, and muscles got smaller, but brain and kidneys didn't change.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Scientific Reports
Year
2025
Authors
K. Falkenhain, Leanne M. Redman, Wendy Y. Chen, Corby K. Martin, Eric Ravussin, Wei Shen
Related Content
Claims (10)
After 24 months of eating fewer calories, changes in metabolism are detectable using detailed body scans like DXA or MRI, but not when using only total body weight.
When you repeatedly eat fewer calories but still get all the good nutrients, your body adjusts to burn energy more efficiently and becomes less resistant to losing weight.
When healthy, normal-weight people eat 25% fewer calories for two years, they lose weight—but their bodies also burn even fewer calories at rest than you’d expect just from losing weight, as if their metabolism slows down on its own.
When healthy people eat 25% fewer calories for two years, their liver, heart, and muscles shrink a bit, which helps their body adjust to less food—but their brain and kidneys stay about the same size as people who eat normally.
Even when you're sitting still, your liver and heart are burning a lot of energy—more than other organs—so the bigger these organs are, the more calories your body uses just to keep them running.
When healthy, normal-weight adults reduce their calorie intake by 25% for two years, their energy use during sleep drops by about 159 kcal per day after one year and 137 kcal per day after two years, more than can be explained by changes in body weight or composition.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.