Caloric restriction
Last reviewed 25 August 2026 · Evidence-graded review — see Methodology
Deliberately eating less, by around 12 percent, improved nearly every cardiometabolic marker measured in a rigorous two-year trial. Cholesterol ratios improved, insulin sensitivity rose and inflammatory markers cooled. Whether it lengthens human life, nobody knows yet.
CALERIE, a multicentre randomised controlled trial in 218 healthy adults of normal to slightly raised weight, asked volunteers to cut 25 percent of energy intake and achieved a sustained 12 percent, which brought meaningful weight loss along with improved LDL cholesterol, total-to-HDL cholesterol ratio, insulin sensitivity and blood-pressure-related measures (Kraus et al., Lancet Diabetes Endocrinol 2019). A companion analysis found resting metabolism slowed more than weight loss alone could explain and oxidative damage to cells declined, hints of mechanisms long seen in animal work arriving in humans (Redman et al., Cell Metab 2018). It grades moderate for clear reasons: the endpoints are risk markers rather than years lived, the achieved dose was half the intended one, and lifelong adherence at this level is unproven outside a supervised trial. Deliberate undereating also carries real risks for some people, listed under who this is for.
Doing it: Consider it only if your BMI sits between 22 and 28, you have no history of disordered eating, and you can hold weight stable while doing it. A realistic version is trimming around 300 kcal of low-nutrient calories a day while keeping protein up. If you take diabetes or blood-pressure medication, do this only with your doctor involved.
Who it suits: Healthy-weight adults genuinely interested in it, ideally with periodic check-ins; not appropriate if you are underweight, frail, pregnant, or have any history of disordered eating
Sources
- Kraus WE, et al. 2 years of calorie restriction and cardiometabolic risk (CALERIE): exploratory outcomes of a randomised controlled trial. Lancet Diabetes Endocrinol 2019.
- Redman LM, et al. Metabolic Slowing and Reduced Oxidative Damage with Sustained Caloric Restriction. Cell Metab 2018.
Next in diet: Plant-based diet →
Prefer to start with what a blood test can tell you? All 48 diagnostic tests, ranked →