Young adults who follow a diet that is low in calories but nutritionally sound for six months appear to lose weight and fat without significant bone loss, according to a report in the September 22 issue of Archives of Internal Medicine, one of the JAMA/Archives journals.
Calorie restriction is the only intervention known to decrease the rate of biological aging and increase longevity, according to background information in the article. However, it is well known that chronic energy deficiency impairs bone mineral uptake and that weight loss is associated with bone loss in obese individuals. Calorie restriction, therefore, could also lead to bone loss and fracture.
Leanne M. Redman, Ph.D., and colleagues at
After six months, average body weight was reduced by 1 percent in the control group, 10.4 percent in the calorie restriction group, 10 percent in the calorie restriction plus exercise group and 13.9 percent in the low-calorie diet group.
Bone mineral density and blood markers of bone resorption and formation (processes by which bone is broken down and regenerated on a regular basis) were measured at the beginning of the study and again after six months. “Compared with the control group, none of the groups showed any change in bone mineral density for total body or hip,” the authors write. Markers of bone resorption were increased in all three intervention groups, while markers of bone formation were decreased in the calorie restriction group but were unchanged in the low-calorie diet or calorie restriction plus exercise group.
“Our data do not support the notion that extreme weight loss (more than 10 percent) over short periods (three months) has a worse prognosis on bone health than gradual weight loss achieved over six months by moderate calorie restriction with or without aerobic exercise,” the authors write. “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.”
Arch Intern Med. 2008;168:1859-1866.