Effect of weight change on bone mass in female adolescents.

The purpose of this study was to examine changes in bone mineral density/bone mineral content (BMD/BMC) in obese female adolescents (Tanner stages 2 to 4) pursuing a weight reduction program. This was a prospective pilot clinical investigation involving 92 obese females screened to meet inclusion criteria and required to participate in a 6-month weight loss intervention. Baseline, 6 months, and 12 months measurements were taken for total body/lumbar spine BMD/BMC and percentage body fat. Survey instrumentation included the following: calcium food frequency/24-hour dietary recall, physical activity, and psychological assessments for anxiety/self-esteem. Changes in bone measurements were compared with changes in body weight measurements using multiple linear regression. Other potentially confounding variables analyzed included bone area, calcium intake, baseline Tanner stage, activity level, and height. Total body/lumbar spine BMD/BMC changes were found to be most significantly correlated with weight changes in the subject population. Although mean weight increased, the rate of increase per a given height velocity slowed to an appropriate height for weight ratio. Individuals who lost weight did not lose BMD/BMC; however, the rate of growth declined when compared with all study subjects whose bone growth rate was consistent with normal weight female adolescents. In this study, weight changes were strongly related to bone measurement changes in an obese adolescent female population. Dietitians counseling obese young girls are encouraged to emphasize the importance of a healthy weight loss program with optimal calcium intake and inclusive of weight-bearing exercises.