Effects of the Two Types of Anorexia Nervosa on Bone Metabolism

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Patients with anorexia nervosa binge eating/purging had moderately higher areal bone mineral density at the radius and lumbar spine.
Patients with anorexia nervosa binge eating/purging had moderately higher areal bone mineral density at the radius and lumbar spine.

The profile characteristics of the 2 types of anorexia nervosa (binge eating/purging and restrictive) show a significant effect on bone metabolism, and the positive association between resting energy expenditure and areal bone mineral density (aBMD) in anorexia nervosa reinforce the idea that bone metabolism and energy disposal are strongly interdependent, according to a study published in Clinical Endocrinology.

The study recruited 286 females with anorexia nervosa, 204 with restrictive type and 82 with binge eating/purging type from the Endocrinology Department of Montpellier University Hospital in France.

A control group of 130 normal-weight, healthy females without a history of anorexia nervosa or other mental illness were recruited to establish normative values.

The study's objectives were to first compare the profiles of restrictive anorexia to binge/purge anorexia in regard to metabolic markers, gynecological status, body composition, and disease history; and second, to evaluate the possible effect of these characteristics on bone metabolism.

Study findings demonstrate that individuals with restrictive anorexia present with more severe undernutrition than those with binge/purge anorexia, characterized by lower body mass index, resting energy expenditure, whole body fat-free soft tissue, and percentage of body fat mass.

These factors were demonstrated to have a negative association on aBMD, with binge/purge anorexia participants having a higher bone mass than restrictive anorexia participants. The fact that the aBMD differences disappeared after analyses were adjusted for age, body weight, and use of hormonal contraceptives suggest that better preservation of weight and body composition results in better preservation of bone mass in females with anorexia nervosa.

Study investigators conclude, “Globally, aBMD in the two subgroups was influenced by such well-identified common factors as weight, lowest [body mass index], and duration of [anorexia nervosa] or amenorrhea. Moreover, we report for the first time a positive correlation between [resting energy expenditure] and aBMD, which reinforces the concept that energy stores and bone metabolism are strongly interdependent.”

Reference

Maïmoun L, Guillaume S, Lefebvre P, et al. Effects of the two types of anorexia nervosa (binge eating/purging and restrictive) on bone metabolism in female patients[published online April 6, 2018]. Clin Endocrinol. doi: 10.1111/cen.13610

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