Changes in bone mineral content in obese dieting women

Significant reductions in total-body bone mineral density (BMD) have been reported in obese women who consume very-low-calorie diets. A reduction in bone mass is highly correlated with an increased risk of osteoporosis. The present study investigated whether strength training would prevent such reductions in dieters. Twenty-one healthy obese women weighing (mean +/- SD) 91.1 +/- 9 kg and aged 38 +/- 9 years were randomly assigned to receive either diet alone or diet plus resistance training. Both groups consumed a 925-kcal/d portion-controlled diet for the first 16 of 17 weeks and a 1,000 to 1,500-kcal/d balanced deficit diet thereafter. Bone mineral content (BMC), BMD, fat-free mass (FFM), and fat mass were measured with dual-energy x-ray absorptiometry (DEXA) before and after 24 weeks of dieting. No significant changes in total-body or lumbar spine BMC and BMD were observed in either condition at the end of treatment. However, both groups demonstrated a significant loss of both BMC and BMD in the femoral neck and greater trochanter. Diet plus resistance training was not associated with a significantly better outcome on either of these measures versus diet alone. The results suggest that increasing the energy content of very-low-calorie diets to 925 kcal/d may prevent the loss of total BMD, but not the loss from the femoral neck and greater trochanter. These findings raise a concern in light of the high frequency of dieting in American women.