Metabolic assessment of menstruating and nonmenstruating normal weight adolescents.

Objective: Resumption of menses (ROM) is a key indicator of recovery in AN, but patients may remain amenorrheic despite weight restoration. The objective of this study is to better understand the mechanism of amenorrhea in patients with eating disorders.

Method: A retrospective chart review was conducted of 382 normal weight adolescents with a history of anorexia nervosa, bulimia nervosa, or eating disorder not otherwise specified, who had been referred for indirect calorimetry tests. Resting energy expenditure (REE) was compared between amenorrheic (n = 60) and regularly menstruating females (n = 121).

Results: Participants with amenorrhea had a mean REE of 1,103 kcal/24 h (79% predicted), whereas participants who were menstruating regularly had a mean REE of 1,217 kcal/24 h (85% predicted; p = 0.001). The amenorrheic group was found to be at a lower mean body weight (53.7 +/- 5.6 kg vs. 57.5 +/- 7.4 kg; p < or = 0.001), at a lower percent ideal body weight (98.5 +/- 8.3% vs. 102.8 +/- 10.2%; p = 0.005), and at a lower BMI (20.5 +/- 1.7 vs. 21.5 +/- 2.2; p = 0.002).

Discussion: This study highlights that amenorrheic participants with a history of eating disorders who are at normal body weight are hypometabolic, suggesting an adaptive response to dietary restriction.