Calorie restriction diet not linked to bone loss

NEW YORK (Reuters Health) - A calorie restriction diet does not cause bone loss in young, overweight adults, provided adequate amounts of calcium and other nutrients are maintained, according to a report in the Archives of Internal Medicine.

The aim of a calorie restriction diet is to reduce daily calories by 20 to 40 percent compared with the average intake, while still maintaining optimal nutrition. As such, it is sometime referred to as CRON, for "calorie restriction with optimal nutrition."

"Our data do not support the notion that extreme weight loss (more than 10 percent of body weight) over short periods (3 months) has a worse prognosis on bone health than gradual weight loss achieved over 6 months by moderate calorie restriction with or without aerobic exercise," Dr. Leanne M. Redman, from Pennington Biomedical Research Center in Baton Rouge, Louisiana, and colleagues conclude.

These results are based on a study of 46 subjects who were randomly assigned to one of four diets: a normal healthy diet; a 25-percent calorie restriction diet; a 25-percent calorie restriction plus aerobic exercise diet; or a low-calorie diet followed by weight maintenance.

The average loss of body weight ranged from 1.0 percent with the healthy diet to 13.9 percent with the low-calorie diet. With the calorie restriction diet, the average loss was 10.4 percent, and with the calorie restriction with aerobic exercise, it was 10.0 percent.

Compared with the healthy diet, none of the other diets were associated with significant changes in bone thickness.

"We speculate that in young individuals undergoing calorie restriction, minor adjustments in bone occur as a normal physiological adaptation to the reduced body mass." They suggest that longer studies are needed to confirm that "bone quality is preserved with weight loss," the authors conclude.

SOURCE: Archives of Internal Medicine, September 22, 2008.