Nutrition
Calorie restriction
Calorie restriction without malnutrition is the oldest and most-replicated lifespan intervention in laboratory animals. CALERIE, the flagship human trial, tested two years of sustained restriction in healthy non-obese adults — measuring cardiometabolic risk factors, because human lifespan cannot be measured in a two-year trial.
Quick verdict
In the main randomised human trial, two years of sustained calorie restriction improved cardiometabolic risk factors in healthy non-obese adults. Whether decades of restriction would extend human life is unmeasured — and the regimen's demands and risks make it far from a casual recommendation.
The assessment
Claim by claim
Each claim is graded on its own evidence. A grade for one claim says nothing about the others.
| Claim | What was measured | Evidence |
|---|---|---|
| Improves cardiometabolic risk factors in healthy non-obese adults | Surrogate biomarker | Early |
| Extends human lifespan | Lifespan | Insufficient |
Improves cardiometabolic risk factors in healthy non-obese adults
Early human evidenceOutcome measured: Surrogate biomarker — A laboratory marker measured as a stand-in for health. A change here does not by itself demonstrate a health benefit.
CALERIE randomised 218 healthy non-obese adults to around 25% intended calorie restriction or usual diet for two years. Achieved restriction averaged about 12%, and multiple cardiometabolic risk factors improved.
Why this grade — the appraisal in full
One or a small number of small, short or preliminary human studies. Directionally interesting, not yet dependable.
- Strongest study design. Randomised controlled trial with 218 participants.
- Human research volume. 1 human study, 218 participants in total.
- What was measured. Human studies measured surrogate biomarkers only. A change in a marker is not by itself a demonstrated health benefit.
- Replication. The supporting result has not been independently replicated in humans.
- Study duration. Longest human study ran 104 weeks.
Limitations. Risk factors are surrogates: the trial demonstrates physiological change, not longer life. Adherence below target illustrates how demanding sustained restriction is outside a trial.
| Study | Design | Population | Finding |
|---|---|---|---|
| [1]2 years of calorie restriction and cardiometabolic risk (CALERIE): exploratory o…The lancet. Diabetes & endocrinology · 2019 · PMID 31303390 | Randomised controlled trialHuman | 218 participantsHealthy participants | Supports the claimCALERIE phase 2: sustained CR improved cardiometabolic risk factors over two years. |
Extends human lifespan
Insufficient evidenceOutcome measured: Lifespan — Death from any cause was measured.
No human study has measured whether calorie restriction extends lifespan; the animal literature is strong but species-dependent, with even primate studies disagreeing between sites.
Why this grade — the appraisal in full
Too little credible research exists to judge the claim either way.
- Available research. No usable studies are linked to this claim.
Limitations. A definitive human lifespan trial is practically impossible; the question will be answered, if at all, through intermediate endpoints and long observation.
Human evidence
1 study in people.
- [1]Randomised controlled trial · 218 participants
Animal and laboratory evidence
Shown separately, and never used to support a human claim.
No preclinical study is currently linked on this page.
Before anything else
Safety and interactions
Sustained restriction risks bone density loss, lean mass loss and, in susceptible people, disordered eating. It is unsuitable for many groups, and CALERIE participants were carefully screened and monitored.
The ledger
Grade history
No grade on this page has changed since tracking began. When one moves — a new trial, a retraction, a corrected appraisal — the change is detected automatically and recorded on the public ledger.
Falsifiability
What would change our view
Long-term human data on hard outcomes, or validated intermediate endpoints tightly linked to them. Better characterisation of who is harmed by restriction matters as much as who benefits.
Check everything
Sources
Every citation links to its PubMed record. Bibliographic details are retrieved from PubMed, not written by us.
- [1]2 years of calorie restriction and cardiometabolic risk (CALERIE): exploratory outcomes of a multicentre, phase 2, randomised controlled trial Kraus WE et al.. The lancet. Diabetes & endocrinology. 2019. PMID 31303390 · doi:10.1016/S2213-8587(19)30151-2