New research does not support the general belief that obesity increases bone mass and is therefore good for bone health. A study, in which investigators corrected for the mechanical loading effect of increasing body weight, suggests the opposite.

“Our study found that increasing body fat mass decreases bone mass, for people of similar weight,” Dr. Hong-Wen Deng from University of Missouri-Kansas City told Reuters Health. “Therefore, increasing obesity (fat mass) is not good for bone health.”

The finding is “important,” Deng and colleagues say, because it suggests that interventions or treatments aimed at reducing obesity may increase bone mass and thus protect against osteoporosis.

Past studies on the relationship between obesity and osteoporosis did not control for the “mechanical loading effects” of a person’s total body weight on bone mass, the investigators note in a report published this month.

Deng’s team reevaluated the relationship between obesity and osteoporosis taking into account mechanical loading effects of total body weight on bone mass in more than 6,400 healthy adults.

According to the investigators, when the mechanical loading effect of body weight on bone mass was adjusted for, fat mass was negatively associated with bone mass; that is, in general, the greater the fat mass, the lower the bone mass.

The results of their study, the researchers say, also “reaffirm the beneficial effects of appropriate weight-bearing and mechanical loading on a healthy skeletal system.”

SOURCE: The Journal of Clinical Endocrinology and Metabolism, May 2007.