Mouse study: When it comes to living longer, it's better to go hungry than go running

• Both exercise and caloric restriction moderated the level of 8-hydroxyguanosine (8-OHdG), a marker of DNA damage. Among the animals that ate all they wanted, those that did not exercise had the highest levels of 8-OHdG and those that exercised had much lower levels. The researchers concluded that DNA damage increases with age and is accelerated by obesity but could be slowed by caloric restriction and/or exercise. The researchers noted, however, that the results may differ if they had used older mice or subjected them to greater caloric restriction than the mild (9% fewer calories) or moderate (18%) restriction this study employed.
  
  

Overall, these findings indicate that the physiological stress of exercise did not produce enough damage to tissues or DNA to explain why exercise does not lengthen life span. Instead the study suggests that caloric restriction creates beneficial changes in the body’s hormone levels which exercise does not. The researchers concluded that these metabolic changes play a role in extending life.

A handful of studies comparing calorie restricted people to people who are avid exercisers, found similar hormonal benefits among those eating less. However, calorie restriction studies are difficult to carry out in people because participants often complain of feeling hungry, lethargic, and cold.

Huffman also emphasized that the benefits of exercise may be greater for humans than for mice because people are more prone to develop cardiovascular diseases, and exercise is particularly good at warding off those diseases. Mice tend to die of kidney disease and cancer, Huffman said.

“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.”

NOTE TO EDITORS: To interview Dr. Huffman, please contact Christine Guilfoy at (301) 634-7253 or at .

Physiology is the study of how molecules, cells, tissues and organs function to create health or disease. The American Physiological Society (www.The-APS.org/press) has been an integral part of this discovery process since it was established in 1887.