Body composition and resting energy expenditure in women with anorexia nervosa: Is hyperactivity a protecting factor?

Background: In subjects with anorexia nervosa (AN) physical exercise may cause or even prevent weight loss, body composition alterations and adaptive thermogenesis. To investigate the influence of behavioral patterns on body composition and energy expenditure in women with AN, we conducted a retrospective analysis in 62 patients with AN referring to our outpatients’ clinic.

Materials and methods: We assessed anthropometric measurement of weight, height, and BMI; body composition was assessed by bioelectrical impedance analysis; resting energy expenditure was measured through indirect calorimetry. Patients’ characteristics were assessed at the time of first evaluation.

Results: The subjects were both restricting type (ANR, n = 39) and binge-eating/purging type (ANBP, n = 23) according to DSM-5. We observed a lower reactance (58.63 (11.9) vs. 66.5 (15.5) Ohm, p < 0.05) and higher total body water in ANR subjects. No differences were found in phase angle, fat mass or fat-free mass, nor in REE measures. Within ANR subgroup, we identified two behavioral patterns, with or without physical hyperactivity. Compared to dieting and fasting subjects, hyperactive subjects showed higher phase angle [5.6 (0.7) vs. 4.8 (0.8), p < 0.05], lower fat-free mass [82.5 (6.8) vs. 89.9 (7.5)%, p < 0.05], greater proportion of fat mass [17.5 (6.8) vs. 10.1 (7.5)%, p < 0.05] and body cell mass [46.6 (5.1) vs. 42.5 (5.5)%, p < 0.05]. Finally, hyperactive subjects had greater BMI than dieting or fasting subjects [18.2 (1.7) vs. 15.8 (1.7), p < 0.005].

Conclusion: With limitations due to the small sample size, hyperactive subjects show body composition and energy metabolism features that seem protective in terms of prognosis.