Body composition in adolescents with anorexia nervosa.

Background: Malnourished patients with anorexia nervosa have altered body composition characterized by depletion of fat and fat-free mass.

Objectives: The objectives of this study were to assess the body composition of adolescents with anorexia nervosa compared with that of control subjects and to investigate the relation between simple anthropometric measures and reference techniques for measuring body composition.

Design: Twenty-three adolescent females with anorexia nervosa aged 15.46 +/- 1.34 y (x +/- SD) were studied. Body composition was measured by anthropometry, dual-energy X-ray absorptiometry (DXA) (for body fat), and prompt gamma in vivo neutron activation analysis [for total body nitrogen (TBN)]. Twenty-five female subjects provided the control DXA data. TBN measurements were compared with prediction equations based on sex, height, age, and weight.

Results: Anorexia nervosa patients had significantly lower weight (40.2 +/- 4.6 kg), body mass index (in kg/m(2): 15.3 +/- 1.2), percentage of body fat (DXA) (13.8 +/- 5.8%), percentage of TBN predicted for age (73 +/- 10%), trunk fat (2.1 +/- 1.0 kg), leg fat (2.6 +/- 1.1 kg), and trunk-to-leg fat ratio than did control subjects (P < 0.05). In anorexia nervosa patients, significant correlations were found between triceps skinfold thickness and percentage of body fat (r = 0.83), body mass index and percentage of body fat (r = 0.46), and body weight and TBN (r = 0.84, P < 0.05).

Conclusions: Hospitalized adolescent females with anorexia nervosa are depleted of total body fat and protein. We identified 3 simple anthropometric measures (triceps skinfold thickness, BMI, and body weight) that can be used to assess body composition and nutritional status in malnourished adolescents with anorexia nervosa.