NEW YORK (Reuters Health) – Dieting with calorie restriction does not cause significant 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 for September 22.

“Our data do not support the notion that extreme weight loss (more than 10%) 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.

The results are based on a study of 46 subjects (average age 37 years) who were randomized to one of four diet groups: healthy diet (control); 25% calorie restriction from baseline energy requirements; 25% energy deficit through calorie restriction plus increased aerobic exercise; and low-calorie diet (890 kcal/day; goal, 15% weight loss) followed by weight maintenance.

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

Compared with the healthy diet, none of the other diets were associated with significant changes in overall or hip bone mineral density. Bone resorption markers, however, were increased with the intervention diets relative to the healthy diet. Bone formation markers were decreased in the calorie restriction group, but were unchanged in the other groups.

“We speculate that in young individuals undergoing calorie restriction, minor adjustments in bone occur as a normal physiological adaptation to the reduced body mass. Further studies of longer duration are warranted and should include an assessment of bone architecture to ensure that bone quality is preserved with weight loss,” the authors conclude.

Arch Intern Med 2008;168:1859-1866.