Despite usual onset during adolescence the cause of low bone density in adolescent onset anorexia nervosa is incompletely understood. Puberty is known to be a crucial time for the development of peak bone mass, due principally to growth plate bone formation and modelling on preformed surfaces. This results in bone formation uncoupled from bone resorption leading to increased bone size due to increase in matrix and bone mineral content. It was hypothesized that low bone density in adolescent anorexia nervosa was caused by malnutrition during puberty suppressing normal bone matrix formation at all sites of bone formation thus arresting bone mineralization. Method 49 female adolescents with anorexia nervosa and 109 healthy female adolescent controls were studied. 22 of the anorexia nervosa subjects were studied again a year later. Bone area, mineral content and density were measured using Dual Xray Absorptiometry at the spine, hip and whole body sites, including body composition assessment. Estimated volumetric bone density was calculated using published equations in order to study bone density independent of bone size. Height, weight and Tanner stage in puberty were measured. Dietary intake and physical exercise were assessed using questionnaires. In a subset of anorexia nervosa and control subjects bone age was measured. In a subset of anorexia nervosa subjects bone formation was assessed using serum bone specific alkaline phosphatase and osteocalcin, and bone resorption was assessed using urine N-telopeptide.

Unauthorized reproduction of this 8 article is prohibited. Objective:To examine differences in bone mass between children and adolescents swimming competitively at nonelite levels (locally and regionally) and nonathletes and to assess changes in bone mass in these 2 groups over 24 months after taking into consideration several known confounders of bone mass.Design:Observational prospective study.Participants:White nonelite swimmers (n=128) and nonathletes (n=106) 8 to 18 years of age from Memphis, Tennessee, USA.Main Outcome Measures:Participants underwent dual-energy x-ray absorptiometry to assess total body and hip bone mineral content (BMC) at baseline and 12 and 24 months later.Results:At baseline, swimmers had 4.2% and 6.1% higher adjusted BMC for the total body and hip, respectively, compared with nonathletes (P values < 0.027). Averaging across assessment points, swimmers had 73.5 and 2.2 g higher BMC for the total body and hip, respectively, than nonathletes. Although there was a significant annual increase in total body and hip BMC in both groups (33.5 and 0.7 g, respectively), there was no difference in annualized bone accrual between swimmers and nonathletes for either total body BMC (swim by time effect; P=0.213) or hip BMC (P=0.265).Conclusions:Competitive swimming at nonelite levels during childhood and adolescence does not seem to compromise bone accrual.