Results from a controlled clinical trial indicate that overweight people who cut their calories by 25 percent for six months have reduced fasting insulin levels and core body temperature—two markers associated with increased longevity in humans. The study is part of a project sponsored by the NIH's National Institute on Aging (NIA) to learn more about the effects of sustained low-calorie diets in humans on factors affecting aging.
This type of intervention—maintaining a substantial percent reduction in caloric intake—has been shown to substantially extend the longevity of laboratory rodents if sustained over much of the animal's life span. Effects of such an intervention on human aging are not yet known.
The study, part of the NIA-supported Comprehensive Assessment of Long-Term Effects of Reducing Intake of Energy (CALERIE), was conducted by Leonie K. Heilbronn, Ph.D., Eric Ravussin, Ph.D., and colleagues at the Pennington Biomedical Research Center of Louisiana State University in Baton Rouge.
The low-calorie diet also resulted in changes in some, but not all, of the metabolic factors that have been related to longevity or aging. That study is a pilot project for a longer CALERIE trial expected to start in the autumn of 2006 at three U.S. locations to test effects of lowering caloric intake for two years.