Calorie Restriction and Aging

What did calorie restriction change in the CALERIE trial?

September's renewed discussion of longevity interventions raises a practical question: how strong is the evidence for changing how much we eat? Calorie restriction offers one example with randomized human research behind it, although the central findings predate the latest headlines. [Medical News Today coverage](https://www.medicalnewstoday.com/amp/articles/what-can-and-cant-slow-down-aging-new-study-offers-clues).

In CALERIE, participants assigned to reduce calories aimed for a 25% decrease but achieved approximately 12% over two years. A 2019 analysis reported improvements in blood pressure, LDL cholesterol and insulin sensitivity. These are clinically relevant risk factors, but their improvement does not establish that participants experienced fewer heart attacks or lived longer. The study involved healthy younger and middle-aged adults, limiting what it can tell us about older or frail populations. [CALERIE cardiometabolic findings](https://pubmed.ncbi.nlm.nih.gov/31303390/).

Did eating fewer calories actually slow biological aging?

Researchers subsequently examined DNA methylation, chemical markings on DNA that can be used to calculate aging-related scores. Their 2023 analysis found that calorie restriction modestly slowed DunedinPACE, an algorithm designed to estimate the pace of biological aging. Two other measures, PhenoAge and GrimAge, showed no significant change. These different results underline that aging tests capture different biological signals. [Nature Aging analysis](https://www.nature.com/articles/s43587-022-00357-y).

The analysis was conducted after the original trial and evaluated biomarkers rather than lifespan. Its findings therefore cannot tell an individual how many extra healthy years a dietary change might provide. The authors identified longer follow-up, including measurements of chronic disease and mortality, as necessary to establish whether the observed biological changes translate into lasting benefits. [Study findings and limitations](https://www.nature.com/articles/s43587-022-00357-y).

Should people restrict calories to improve longevity?

Calorie restriction in research means reducing energy intake while maintaining essential nutrients. It differs from fasting, which primarily changes when people eat. The National Institute on Aging's explanation of CALERIE also describes tradeoffs: participants experienced modest declines in bone density and lean body mass, and some had temporary anemia. These findings support clinical monitoring. [NIA evidence review](https://www.nia.nih.gov/news/calorie-restriction-and-fasting-diets-what-do-we-know).

Anyone considering a substantial dietary change should discuss nutritional needs and health conditions with a clinician or registered dietitian. Results from younger adults cannot establish safety for older people vulnerable to malnutrition. For healthy aging, NIA emphasizes nutritious food, regular physical activity, adequate sleep, social connection and avoiding smoking. [NIA guidance](https://www.nia.nih.gov/news/calorie-restriction-and-fasting-diets-what-do-we-know).