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Eat less, live more

Animal trials suggest that calorie restriction may extend lifespan. This is the longest human trial conducted thus far on the topic, and serves to inform calorie restriction’s health impacts and feasability.

Study under review: A 2-Year Randomized Controlled Trial of Human Caloric Restriction: Feasibility and Effects on Predictors of Health Span and Longevity

Introduction

Short of discovering the fountain of youth, are there ways to live longer?

Some think that caloric restriction is an answer. Caloric restriction is defined as lowering caloric intake without depriving oneself of essential nutrients. There is lots of evidence[1] in animals that suggests caloric restriction increases lifespan in many, but not all, species. Observational evidence[2] in people who voluntarily practice long-term caloric restriction corroborates some of the animal evidence. Humans undergoing caloric restriction seem to mimic some of the physiological changes seen in other animals, and risk factors for several disease markers seem to improve in humans undergoing caloric restriction as well.

However, observational studies can only show correlation, not causation. Long-term, controlled clinical studies are needed to show causation. These are very hard and very expensive to conduct for the time needed to actually observe the effects of caloric restriction on mortality. Not to mention the fact that it would be hard to find people who would be willing and able to enroll in such a trial!

A compromise is possible, though. A randomized, controlled clinical trial on the order of months or years that examines markers for disease and longevity would be able to tell us something about how caloric restriction affected those markers. And if those markers correlated well with mortality, we’d be able to take a better educated guess at how these diets may affect longevity. Such a trial would also give us a better idea of whether calorie-restricted diets could be maintained for the medium term, since the self-selection bias which may exist in observational studies would be mitigated.

That’s the purpose of the study under review.

Evidence from animal models suggests that calorie-restricted diets can increase longevity in many, but not all, species. There is some observational evidence suggesting this effect exists in humans as well. This controlled clinical trial’s purpose was to examine how a calorie-restricted diet affects markers of disease and longevity in humans, as well as to test the feasibility of a calorie-restricted diet.

Who and what was studied?

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What were the findings?

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