For American adults battling the bulge, the key to losing those extra pounds is often exercise and eating a lower-calorie diet. But a drop in body weight, while improving overall health, also can lead to decreased bone density, increasing the risk of developing weakened bones. The chances for hip fractures also go up as bone mineral density goes down.

Recent research published in the Archives of Internal Medicine evaluated the effects of weight reduction on bone loss. The findings? Folks who lose weight by slashing calories alone also may be losing bone mineral density. But weight loss through physical activity does not appear to produce the same bone-loss effect.

Researchers studied the effects of weight loss on bone health in forty-eight U-S adults– thirty of them women, and the rest men. The study participants were separated into three groups. One followed a calorie-restricted diet, the second ate the same amount of food but began an exercise program and the third only received healthy lifestyle information.

The study revealed no significant changes in bone density in the exercise or healthy lifestyle groups. But bone scans in individuals in the calorie-restriction group showed an average loss of two-point-two percent of hip bone density, and two-point-one percent at the top of the femur— both high-risk fracture sites. The lesson learned? Middle and older age adults striving to drop pounds might want to include bone-density friendly exercise in their weight loss regimen.