Physiological and Cardiac Effects of Weight Loss in Adolescents With Atypical Anorexia Nervosa Versus Those Undergoing Bariatric Surgery: A Retrospective Comparative Study.

OBJECTIVE: Adolescents with atypical anorexia nervosa (AAN) experience cardiac complications at rates comparable to typical anorexia nervosa, despite remaining within or above a normal weight range. The physiological mechanisms underlying this paradox remain poorly understood. This study is the first to compare cardiac outcomes between adolescents with AAN and those who underwent bariatric surgery, a population experiencing similarly rapid and substantial weight loss within a medically supervised context. METHODS: A retrospective study compared adolescents with AAN (n = 102, 82% female, mean age 15.0 ± 1.6 years) and adolescents who underwent bariatric surgery (n = 90, 67% female, mean age 16.4 ± 1.1 years) on weight loss magnitude and pace, minimum heart rate, thyroid function, physical activity and laboratory indices. RESULTS: Despite losing more weight at a faster rate, the bariatric surgery group had significantly higher minimum heart rates (83.6 vs. 62.2 bpm, p < 0.001) and no cases of clinically significant bradycardia, compared with 22.5% in the AAN group. Rate of weight loss did not correlate with minimum heart rate in either group. Exploratory analyses suggested an association between T3 levels and minimum heart rate, warranting further investigation. CONCLUSION: Weight loss magnitude and rate alone do not determine cardiac risk in AAN. The nutritional context and physiological adaptations specific to eating disorders appear to have a role in the cardiac outcome. Adolescents with AAN require proactive cardiac monitoring regardless of current weight or pace of weight loss.