Denise Grady of The New York Times reports low-calorie diets may lead to longer life. Although due to the difficulty of conducting a large-scale/long-term study, there is no proof a low-calorie high-nutrient diet can prolong human life. But a new study hopes to change that:
A six-month study in 48 people directed by Dr. Ravussin, being published today in The Journal of the American Medical Association, is the first rigorous test of calorie restriction in people who are overweight but not obese. Most participants reduced calories by 25 percent, but some cut back more and ate only 890 calories a day for several months.
"There's never been a study like this one," said Dr. Evan Hadley, director of geriatrics and clinical gerontology at the National Institute on Aging, which paid for the study. He called the results "striking," even though the experiment was only a pilot study for a two-year trial of calorie restriction due to begin in the fall.
Among the main findings of Dr. Ravussin's study was that calorie restriction led to decreases in insulin levels and body temperature. Both are considered signs of longevity, partly because an earlier study by other researchers found both traits in long-lived people. The diet also led to a drop in thyroid hormones and declines in DNA damage.
But Dr. Ravussin and Dr. Hadley cautioned that the study was preliminary, and that it did not prove that calorie restriction could make people healthier or add years to their lives.
"It's an important step along the way," Dr. Hadley said.