Predicting Menstrual Recovery in Adolescents With Anorexia Nervosa Using Body Fat Percent Estimated by Bioimpedance Analysis

Objective: To identify the threshold of total body fat percentage (TBF%) required for the resumption of menses (ROM) in hospitalized female adolescents with anorexia nervosa (AN) using bioimpedance analysis (BIA). Methods: All female adolescents hospitalized with AN in our medical center were evaluated in a longitudinal prospective study during the years of 2012–2017. Anthropometric data, body fat measured by BIA, and hormonal determinants were collected periodically, in addition to routine medical and gynecological assessments. Results: Sixty-two participants presented with secondary amenorrhea, of which 20 remained with amenorrhea and 42 had ROM during hospitalization. At discharge, participants with ROM regained significantly more weight, and had higher mean body mass index (BMI), BMI standard deviation scores, and TBF% than those who remained with amenorrhea. Receiver operating characteristic analysis identified that a TBF% of 21.2% had the highest discriminative ability for ROM (sensitivity = 88%, specificity = 85%, positive predictive value = 93%). Compared with the anthropometric parameters, TBF% had the highest area under curve (AUC =.895), which significantly differed from that of BMI standard deviation scores (AUC =.643, p =.007) and body weight (AUC =.678, p =.03). Conclusions: BIA is a safe and relatively simple method to assess the TBF% required for the return of balanced menstrual cycles in female adolescents with AN. The TBF% with the highest discriminative ability for menstrual resumption as assessed by BIA is 21.2%.