Opposite Changes in the Serum Brain-derived Neurotrophic Factor in Anorexia Nervosa and Obesity

Objective: A role for the brain-derived neurotrophic factor (BDNF) in the regulation of eating behavior has been recently demonstrated. Therefore, the possibility exists that alterations in BDNF production and/or activity are involved in the pathophysiology of anorexia nervosa (AN) and obesity.

Methods: We measured morning serum levels of BDNF in 22 women with AN, 24 women with obesity (body mass index [BMI] > 30 kg/m2), and 27 nonobese healthy women. All the subjects were drug-free and underwent a clinical assessment by means of rating scales measuring both eating-related psychopathology and depressive symptoms.

Results: As compared with the nonobese healthy controls, circulating BDNF was significantly reduced in AN patients and significantly increased in obese subjects. No significant difference was observed in serum BDNF concentrations between AN women with or without a comorbid depressive disorder. Moreover, serum BDNF levels were significantly and positively correlated with the subjects' body weight and BMI.

Conclusion: The BDNF changes observed in AN and obesity are likely secondary adaptive mechanisms aimed at counteracting the change in energy balance that occurs in these syndromes.