Cutting calories may promote longevity by increasing the production of chemicals involved in many critical processes within the body, according to a new study in mice.

Researchers say several studies have shown that calorie restriction extends lifespan in many different types of living organisms, including mammals. But exactly how cutting calories affects longevity is unknown.

A study in the August issue of Ageing Research Reviews showed that a very low-calorie diet is not likely to extend human life by much.

In the current study, published in Science, researchers looked at the effects of calorie restriction on the production of nitric oxide in mice over three to 12 months.

Nitric oxide is a compound produced within the body. It acts as a signaling molecule and regulates a variety of physiological processes such as relaxing the walls of blood vessels. In this study, the researchers looked at nitric oxide produced by endothelial cells, which line the inside of blood vessels.

The results showed that mice that were fed 30 percent to 40 percent fewer calories produced more nitric oxide than those who followed an unrestricted diet.

Calorie restriction also caused the mice to increase production of another chemical messenger that stimulated production of new mitochondria (the main energy source in cells) and increased oxygen consumption and expression of a protein previously shown to play a role in calorie restriction’s effect on life span.

These beneficial effects of calorie restriction were not found in mice that lacked the enzyme necessary to synthesize nitric oxide. Therefore, researchers say the findings suggest that nitric oxide may play a critical role in calorie restriction’s effect on longevity.

Extremely Low-Calorie Diet Won't Extend Life

By Jennifer Warner, reviewed by Louise Chang, MD

SOURCES: Nisoli, E. Science, Oct. 14, 2005; vol 310: pp 314-317. News release, Science. WebMD Medical News: “Extremely Low-Calorie Diet Won't Extend Life.”