Follow-up of bone mineral density and body composition in adolescents with restrictive anorexia nervosa: role of dual-energy X-ray absorptiometry

Abstract

Restrictive Anorexia nervosa (ANR) is an eating disorder (ED) characterized by a low bone mineral content (BMC) and by an alteration in body composition (reduction and abnormal distribution of fat mass-FM and lean mass-LM). The aim of our study was to address whether bone and body composition changes could be influenced by hormonal status and sport in female adolescents with restrictive anorexia nervosa-ANR. Prospective study on 79 adolescents with ANR submitted to Dual Energy X-Ray Absorptiometry-DXA at baseline-T0 and after 12 months-T12. Among the 46/79-58.2% patients that completed the study, we evaluated total and regional FM and LM%, as well as lumbar bone mineral density (BMD) and Z-score, linking them to clinical variables: menarche/amenorrhea/hormonal therapy and physical activity. At T0: body mass index (BMI)=16.4±1.4 kg/m2 with low levels of FM% (21.7±5.7) low BMC in 12/46-26.0% (mean Z-score: -1.21±1.27, with higher values related to physical activity-P=0.001). At T12: a significant increase in BMI-P=0.001, with LM reduction and FM increase (more evident in the trunk-P<0.001); regarding bone, no significant changes were observed, though a tendency in terms of improvement associated with resumption of menses. After 1 year, weight recovery was not associated with a reestablishment of bone values; by contrast, it was associated with an increase and a distortion in FM distribution, more evident in trunk region (potential and adjunctive risk factor for the relapse of the psychiatric condition). The complexity of these clinical findings suggested DXA, a low-dose and low-cost technique, in long-term monitoring of ANR patients.