Effect of aerobic exercise on bone mineral density in overweight adolescents

Objective To analyze the relationship between body composition and bone mineral density in adolescents, and explore the influence of lifestyle intervention on bone mineral density and body composition in overweight adolescents.Methods 117 healthy adolescents (age 11.08-15.17 years, male: female 54:63) were recruited from a high school in urban area of Beijing. Anthropometry data were measured. Bone mineral density (BMD), body muscle mass and body fat percentage were measured by dual-energy X-ray absorptiometry(DEXA). According to BMI, subjects were divided into normal weight group(n=30) and overweight group(n=87). Overweight subjects(BMI 22.4~34.09 kg/m2) were randomly assigned to four groups: diet (D), exercise(EX), diet plus exercise(DEX), and overweight control (C). After 10 weeks of diet or aerobic exercise intervention, changes of those indicators were determined.Results BMD of girls was significantly higher than that of boys(P0.01). Subjects in puberty had higher BMD than that in prepuberty(P0.05). No significant difference was observed between normal weight and overweight group(P0.05). BMD was positively correlated with age, height, weight, BMI, chest circumference, hip circumference, whole body muscle mass(r=0.206~0.329,P0.05), and was not significantly correlated with waist circumference, body and trunk fat rates(P0.05). After the intervention, body and truncal fat rates were significantly decreased in group D, EX and DEX(P0.01), BMD in group EX(P0.01) and DEX(P0.05) were significantly increased, while no significant changes of BMD were observed in group D and C(P0.05). The average increase in BMD of exercise groups (EX+DEX)[(0.017±0.027) g/cm2] was significantly higher than that of non-exercise groups (D+C) [(0.008±0.047)g/cm2](P0.01). However, there was no significant difference between changes in BMD of dietary group (D+DEX) and non-dietary group (EX+C) (P0.05). Conclusion In adolescence, BMD increases with age, height and weight, and has gender difference. BMD is positively correlated with muscle mass, but is not correlated with fat rate. Both effective diet and exercise intervention can reduce body weight and fat, but only exercise can promote BMD increase. Overweight adolescents should take lifestyle intervention including aerobic exercises.