Overweight and obese children have low bone mass and area for their weight

OBJECTIVES: To determine whether girls and boys categorized from body mass index (BMI) values as overweight or obese for their age have lower bone min eral content (BMC) or lower bone area in relation to total body weight than children of normal adiposity. DESIGN: Cross-sectional study in a universit y bone research unit. SUBJECTS: Two hundred girls and 136 boys aged 3-19 y recruited from the gen eral population by advertisement. MEASUREMENTS: Total body BMC (g) and bone area (cm(2)) measured by dual ene rgy X-ray absorptiometry (DXA) in relation to body weight (kg), lean tissue mass (kg) and fat mass (kg) in boys and girls of three different BMI perce ntile groupings: normal weight (BMI < 85th percentile); overweight (85 to 9 4th BMI percentile); obese (greater than or equal to 95th BMI percentile). RESULTS: Obese children had higher BMC, bone area, and fat mass for chronol ogical age than those of normal body weight (P < 0.001). In spite of this t he observed values for age-adjusted total body BMC and bone area relative t o body weight were each lower than predicted values, in both overweight and obese children (2.5-10.1% less, P < 0.05) than in children of lower adipos ity. CONCLUSION: In overweight and obese boys and girls there is a mismatch betw een body weight and bone development during growth: their bone mass and bon e area are low for their body weight.