A new study has found that eating less makes mice live longer - and the benefits of a low-calorie diet are even greater than regular exercise provides.

Although the study authors are quick to point out differences between mice and people - not a favorite habit of this particular blog - previous research on humans reached a similar conclusion: Caloric restriction brings physiological benefits that exercise, by itself, does not.

"We know that being lean rather than obese is protective from many diseases, but key rodent studies tell us that being lean from eating less, as opposed to exercising more, has greater benefit for living longer," said Derek M. Huffman of the Albert Einstein College of Medicine in New York, the lead author of the study that appears in the May issue of the American Journal of Physiology.

Earlier studies had showed that exercise can prevent a premature death from disease in some rats, but does not extend the rats' lifespan. And when comparing high-exercise rats to those that don't exercise but eat much less, the rats that ate less lived the longest.

Huffman and his colleagues designed a study to examine the intertwining roles of exercise and caloric restriction. They found that the physiological stress of exercise did not produce enough damage to tissues or DNA to actually shorten the rodents' life span; but caloric restriction creates beneficial changes in the body's hormone levels that exercise alone does not. The researchers concluded that these metabolic shifts must play a role in extending life.

Huffman also emphasized that the benefits of exercise may be greater for humans than for mice because people are more likely to develop cardiovascular diseases, which exercise combats effectively. The leading causes of death in mice are kidney disease and cancer.

"I wouldn't say this study has direct implications for people right now," Huffman said. "But it shows what physiological changes caloric restriction and exercise produce. We can continue to build upon these findings until we can get a better understanding of how this works in people."