Comparison of total and regional body composition in adolescent patients with anorexia nervosa and pair-matched controls.

Body composition in 31 adolescent girls suffering from anorexia nervosa (AN) was measured at the time of hospitalization in order to assess the muscle/bone relationship as a potential source of the development of osteopenia. Differences in lean tissue, fat and bone mass in total body, weight bearing and non weight bearing limbs were estimated in AN and pair-matched controls aged 14.2 +/- 1.8 years (range: 9-17 years). Further, it was investigated if bone mineral density (BMD) better reflects the muscle/bone relationship than bone mineral content (BMC). At the distal radius parameters measured by peripheral quantitative computed tomography (pQCT) were used to estimate the association of volumetric bone density to bone strength and lean body mass. The correspondence to the same and different body regions was assessed. Total lean mass in the controls was closely related to total body bone mineral content (TBBMC), as was lean tissue and bone mass of the limb subregions (r = 0.82 to 0.93). In contrast, the correlation was significantly lower in AN (r = 0.33 to 0.77). In the controls, the pQCT-derived bone strength was correlated with muscle mass of the forearm (r = 0.78, p < 0.001), but only moderately in AN (r = 0.47, n.s.). Regional lean tissue was 11-20% and fat mass was 56-66% lower in AN (p < 0.01). After adjustment for height, TBBMC was different at p = 0.01. Within the limbs subregions, BMC (but not BMD) was different in both groups only in the upper arm and the thigh. BMC reflected the bone/muscle relationship better than BMD. Intra- and between group regressions gave no significant differences between weight bearing and non weight bearing limbs. In conclusion, the assessment of musculoskeletal factors may be a useful tool to develop individual preventive measures for therapy after recovery of our patients.