The effect of therapeutically induced weight gain on plasma leptin levels in patients with anorexia nervosa.

Previously it was shown that hyperleptinemia ensues from the therapeutically induced weight gain in patients with anorexia nervosa (AN). However, not all studies have been able to confirm this finding. To further investigate leptin secretion during weight gain in AN and potential functional implications serum leptin levels, body mass index (BMI),% body fat, fT3, fT4 and TSH of 18 adolescent AN patients (BMI at admission: 14.4+/-1.2) were examined four times during 11 weeks of re-feeding and compared to 18 weight stable controls. Additionally, serum leptin levels, BMI and % body fat were determined in patients reaching target weight after 11-20 weeks (mean 14.3+/-3) of inpatient re-feeding. At admission patients showed lower lg10 leptin levels (P=0.000) and BMI (P=0.000) than controls. At target weight patients still had significantly lower BMI (P=0.000) and% body fat (P=0.000) than controls but lg10 leptin levels of patients were higher than those of controls when adjusted for BMI and% body fat (ANCOVA, group P=0.038). In patients, correlation coefficients between lg10 leptin levels and BMI increments increased during the 11 weeks of re-feeding. BMI,% body fat and fT3 levels were not significantly correlated to lg10 leptin levels in week 11, however, 53% of the variance of leptin levels (corrected R(2)=0.53, P=0.001) was explained by BMI increments between weeks 7 and 11 (P=0.001) and lg10 leptin level at admission (P=0.002). In conclusion, we confirmed weight gain induced hyperleptinemia in AN. Further research is required to assess if this phenomenon contributes to renewed weight loss.