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Low calorie diets may not be all that they are made up to be. A new study has found that even though low calorie diets have been linked to weight loss and longevity, the calories don't contribute to your life span. "If there's a way to manipulate the human diet to let us live longer, we haven't figured it out yet and it may not exist," said biologist Steven Austad from the University of Texas Health Science Centre, who conducted the analysis. Since 1934, research has shown that lab rats, mice, yeast, fruit flies and round worms fed 10 percent to 40 percent fewer calories than their free-eating peers lived some 30 percent longer. In some studies, they lived twice as long. Such findings have spawned a growing community of believers who seek better health and longer life in calorie-restricted (CR) diets, as promised in the 2005 book "The Longevity Diet," including 5,000 members of the CR Society International.
The research has also prompted companies like Procter & Gamble and Nu Skin Enterprises to develop drugs to mimic the effects of calorie restriction. The new study, from the National Institute on Aging (NIA), part of the U.S. National Institutes of Health, suggests this link doesn't hold true for all species. It found that most of the 57 calorie-restricted monkeys did have healthier hearts and immune systems and lower rates of diabetes, cancer or other ills than the 64 control monkeys. However, there was no longevity pay-off. "You can argue that the calorie-restricted animals are healthier," said Austad. "They have better cholesterol profiles, less muscle loss, less disease. But it didn't translate into greater longevity. What we learn from this is you can un-link health and longevity," added Austad.
The NIA study, launched in 1987, is one of two investigating whether eating just 70 percent of the calories in a standard lab diet extends life in a long-lived primate. The Wisconsin National Primate Research Centre's study, begun in 1989, also uses rhesus monkeys, whose physiology, genetics and median lifespan (27 years) are closer to humans than are the rodents in earlier calorie-restriction research.
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