Associations between exercise, bone mineral density, and body composition in adolescents with anorexia nervosa.

OBJECTIVE: To identify the effect of duration of weight-bearing exercise and team sports participation on bone mineral density (BMD) and body composition among adolescents with anorexia nervosa (AN).

METHOD: We retrospectively reviewed electronic medical records of all patients 9-20 years old with a DSM-5 diagnosis of AN evaluated by the Stanford Eating Disorders Program (1997-2011) who underwent dual-energy X-ray absorptiometry.

RESULTS: A total of 188 adolescents with AN were included (178 females and 10 males). Using multivariate linear regression, duration of weight-bearing exercise (B = 0.15, p = 0.005) and participation in team sports (B = 0.53, p = 0.001) were associated with higher BMD at the hip and team sports (B = 0.39, p = 0.006) were associated with higher whole body BMC, controlling for covariates. Participation in team sports (B = - 1.06, p = 0.007) was associated with greater deficits in FMI Z-score. LBMI Z-score was positively associated with duration of weight-bearing exercise (B = 0.10, p = 0.018) and may explain the relationship between exercise and bone outcomes.

CONCLUSION: Duration of weight-bearing exercise and team sports participation may be protective of BMD at the hip and whole body BMC, while participation in team sports was associated with greater FMI deficits among adolescents with AN.

LEVEL OF EVIDENCE: Level V, descriptive retrospective study.