Lowered intake of calories can increase longevity, claims study
Posted on : Wed, 05 Apr 2006 14:14:00 GMT
Author : Alan Cross
News Category : Health
Eating less can do wonders not only for your waistline but also your longevity, a study, by researchers from Louisiana State University in Baton Rouge, claims. Earlier, a study had shown that keeping mice on a low-calorie diet could help increase their life span, a findings that the new study tested on humans.
“A lot of evidence already exists to suggest that calorie restriction increases maximum life span in several animal species. However, there hasn't been any proof of it being the case in humans. This is the first step toward looking at the beneficial effects of calorie restriction in humans,” said Dr Eric Ravussin, one of the authors of the study.
Under the study, the researchers divided 48 healthy overweight subjects, who were not obese, into four groups. The first group continued with the normal diet while the second was put on a diet with 25 per cent less calories than the daily recommendation. The third group's regimen included lowering of 12.5 per cent calories through diet and increasing expenditure of calories by 12.5 per cent through exercise. The fourth group was put on a very low calorie diet that had only 890 Kcal a day to begin with. This was later hiked marginally to maintain a 15 per cent sustained weight loss.
The researchers tracked the subjects for a period of six months and found that the subjects in the first group lost only one per cent of their body weight. By contrast, the second and the third groups shed around 10 per cent, but those in the last group lost 14 per cent of their body weight.
An analysis of their blood insulin levels after fasting and body temperature showed that those who were on low calorie diets had lower insulin levels and body temperature. “Body temperature and blood insulin levels are markers of longevity like gray hair or wrinkles can be. It has been shown both in animals and humans that those with lower body temperature tend to live longer, and so do those with lower fasting insulin levels,” Ravussin said.
In addition, DNA damage among those who restricted their intake of calories was lesser. “One of the many theories of aging is that there is more DNA damage happening, which is the destruction of genetic information – smokers for example have more DNA damage. So this is a very important information, totally novel in humans, that calorie restriction can reduce DNA damage,” Ravussin added.
Dr Evan Hadley, the director of National Institute of Aging that funded the study, hailed the study as 'striking'. “It's very exciting. It's a step forward but not the whole journey,” he said. Agreed Pennington Biomedical Research Center's Dr Steven Smith. “This is really the first demonstration of this conservation of energy and protection of the body by caloric restriction in humans. This might have implications for the prevention of cancer and other diseases that are related to damaging DNA,” he said.
Some experts, however, expressed skepticism about the findings. “Unfortunately, this study looked at biomarkers, not at actual longevity. Therefore, it is hard to attach any particular significance to it,” said Dr Darin Deen, of Albert Einstein College of Medicine in New York. According to Boston's Beth Israel Deaconess Medical Center researcher Dr Eleftheria Maratos-Flier, the study involved overweight people and so its findings cannot be extrapolated to normal body weight people. “Scientifically, this is not a significant study. The group here was overweight. We already know that diet and weight loss are good for overweight people,” Maratos-Flier said.
Dr Leonie Heilbronn, the lead author of the study, admitted that further research was required. “Longer-term studies are required to determine if these effects are sustained and whether they have an effect on human ageing,” she said.
The findings have been published in the Journal of the American Medical Association.
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