Caloric Restriction and Longevity

Dietary Restriction May Increase Lifespan in Some Species

Aug 27, 2008 Tamara Golden

Caloric restriction, feeding laboratory animals only 70% of their usual caloric intake, is the only intervention demonstrated to extend life span in vertebrate organisms.

Caloric restriction involves eating a diet which provides complete nutritional requirements, but which contains about 30% fewer calories than is usually eaten. To date, this is the only experimental, non-genetic intervention that has increased life span in laboratory vertebrate animals. In the lab, applying caloric restriction to animals such as mice or rats is straightforward. A control group of animals is allowed to eat as much as they want (called the ad libitum group, which means “at will”). The amount of calories consumed by this control group is measured, and the experimental group is provided a diet that contains only 70% of the calories consumed by the ad lib group. Tests can then be done comparing the two groups, to see if they differ with respect to measures of health and fitness, or lifespan. In rodents, caloric restriction reduces cancer incidence and improves glucose sensitivity. In rats and some strains of mice, caloric restriction also increases lifespan (1).

How does caloric restriction work?

Caloric restriction is thought to work by switching the body’s metabolism to a state that conserves energy. This metabolic state might be important for survival in times of food scarcity. In this conservation-oriented metabolic state, it is possible that fewer toxic byproducts of metabolism, such as free radicals, are produced, so less damage occurs over time and the animal is able to live longer. Evidence that this metabolic switch might be conserved across the animal kingdom includes the fact that attempts to limit the food intake of fruit flies, nematodes, and even yeast, may increase the lifespan of these organisms.

Will caloric restriction work in people?

It is not easy to define a calorically restricted diet for people. Would it be 30% less than the USDA recommended 2000 calorie diet? Or, 30% less than a gluttonous diet? It appears that caloric restriction extends lifespan in laboratory-adapted strains of mice that would be considered overweight compared to their wild counterparts. In fact, when mice were caught in the wild and brought into the lab and treated with caloric restriction, they did not live longer, though they did experience reduced cancer incidence and other positive biological responses to the reduced calorie diet (2). It is possible that some of the observed positive effects of caloric restriction might be those already recognized to result from eating a healthy diet and maintaining a non-obese weight.

Research into caloric restriction

There is much interest in determining whether there are ways to mimic the positive effects of caloric restriction without the need to actually eat fewer calories. One line of research has found that a category of enzymes called sirtuins are activated by caloric restriction. A compound found in red wine, called resveratrol, is able to activate these same enzymes and may mimic some effects of caloric restriction (3). This compound was found to extend lifespan in simple organisms such as nematodes and yeast. Extensive research is ongoing to understand the molecular mechanisms of caloric restriction.

References and Further Reading

(1) Weindruch and Wolford (1988) "The Retardation of Aging and Disease by Dietary Restriction". CC Thomas, Springfield, IL.

(2) Harper et al. (2006) "Does Caloric restriction extend life in wild mice?" Aging Cell 5, 441-449.

(3) Wood et al. (2004) "Sirtuin activators mimic caloric restriction and mimic ageing in metazoans." Nature 430, 686-689.

The copyright of the article Caloric Restriction and Longevity in Nutrition is owned by Tamara Golden. Permission to republish Caloric Restriction and Longevity in print or online must be granted by the author in writing.