The term “anti-aging” is popular these days. It’s attached to all sorts of creams, lotions, make-up products, supplements and other items that claim to reverse or slow the signs of aging. Anti-aging diets also exist, but what isn’t known is exactly whether or how such diets might turn back the clock.

In a review of research into dietary interventions that claim to slow or reverse aging, scientists from the University of Washington and Pennington Biomedical Research Center studied several diets purporting to slow aging. Not only did the team want to separate fact from fiction, but they wanted to learn if the diets shared any life-extending mechanisms at the molecular level.

Several of the most popular anti-aging diets — calorie-restricted, time-restricted, protein-restricted and ketogenic diets — were studied.

The most studied life-extending measure is calorie restriction (CR), but not to the point of malnutrition. In laboratory-based research, CR reduced diseases associated with aging, slowed functional decline and increased life span. Data from the population generally align with the theory that eating fewer calories is associated with a longer life.

However, the effects of CR on a person’s life span are dependent on their genetic make-up, and for some people calorie restriction can shorten life span.

Several anti-aging diets have developed from the idea of CR to promote longevity. In an effort to separate fact from fiction, the potential shared traits of several of the most popular anti-aging diets such as calorie-restricted, time-restricted, protein-restricted and ketogenic diets were studied.

Lab studies with mice, flies and yeast have been successful in using such dietary manipulations to delay and even reverse aging at the molecular level, but what is not known is if such diets might slow the aging process in humans.

The studies reviewed have helped scientists have a better understanding of the cellular response to low nutrient availability, as well as the physiological consequences of anti-aging diets. The effects are complicated, but similarities exist across the anti-aging diets.

A common denominator seems to be an enzyme called mTOR that could potentially provide a molecular target for drugs designed to increase longevity and produce years of better health.

Calorie restriction and other anti-aging diets hold promise, but more information is needed before recommending any of them to healthy individuals.

The authors conclude, “Future research directed at clarifying the underlying mechanisms involved in eliciting the longevity-promoting response to CR, and how this differs among individuals, should one day help us realize a true precision geroscience approach.”

The study is published in Science.