Cutting down calories does not prolong life, warns Indian American scientist

January 24th, 2009 - 4:50 pm ICT by IANS  

Washington, Jan 24 (IANS) Cutting down on calories may reduce weight, but it does not necessarily increase one’s life span, warns an Indian American expert. “Today there are a lot of very healthy people who look like skeletons…,” said Raj Sohal, professor at the University of Southern California’s (USC) School of Pharmacy.

He and Michael Forster of the University of North Texas Health Science Centre compared the life span and caloric intake of two genetically engineered strains of mice.

The “fat” strain, known as C57BL/6, roughly doubles in weight over its adult life. That strain benefited from caloric restriction. The “lean” strain, DBA/2, does not become obese, said Sohal.

However, caloric restriction did not extend the life of these mice, confirming previous work by Forster and Sohal.

“Our study questions the paradigm that caloric restriction is universally beneficial,” Sohal said. “Contrary to what is widely believed, caloric restriction does not extend (the) life span of all strains of mice.”

By measuring the animals’ metabolic rate, Sohal and his colleagues came to a deceptively simple conclusion: Caloric restriction is only useful when, as in the case of the obese mice, an animal eats more than it can burn off.

“Your energy expenditure and your energy intake should be in balance,” Sohal said. “It’s as simple as that. And how do you know that? By gain or loss of weight. The whole thing is very commonsensical.”

For humans of normal weight, Sohal strongly cautions against caloric restriction. In a 2003 study, he and Forster found that caloric restriction begun in older mice - both in DBA and leaner C57 individuals - actually shortened life span.

However, Sohal said that obese individuals are probably better off cutting calories than increasing their exercise to make up for overeating. Overly vigorous exercise can lead to injuries and long-term wear and tear, said a USC release.

In other words, it is better to skip the double cheeseburger than to turn up the treadmill after going on a binge.

The results are scheduled for publication in the Journal of Nutrition.

Sohal, who received his Ph.D. in biology from Tulane University, is also the recipient of Irwing S. Wright Award of Distinction by the American Federation for Aging Research and Lifetime Research Achievement Award by the American Aging Association.

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