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.

Leptin is thought to modulate feeding behaviour, body weight and energy metabolism by acting through specific cellular receptors. Derangements of leptin production have been repeatedly reported in patients with anorexia nervosa (AN) or bulimia nervosa (BN), but no information has been provided on the functional status of leptin receptors in these disorders. Therefore, we measured plasma levels of leptin and its soluble receptor (Ob-Re) in a total of 130 women, including 22 patients with AN, 45 patients with BN, 18 patients with the bingeeating disorder (BED), 12 non-binge eating obese women and 33 healthy women. Circulating leptin was drastically reduced in underweight anorexics and normal-weight bulimics, but increased in overweight BED patients and non-binge-eating obese women. Conversely, plasma levels of Ob-Re were significantly increased in patients with AN or BN, but decreased in BED and non-binge-eating obese women. Significant inverse correlations were detected between plasma levels of leptin and those of Ob-Re in all the subject groups, except in nonbinge-eating obese subjects. These results show, for the first time, that opposite modifications occur in circulating levels of leptin and Ob-Re across the eating-disorder spectrum. The relevance of these findings to the pathophysiology and treatment of eating disorders remains to be elucidated.

These findings support the view that polymorphic variants of the 5HTT promoter region do not play a part in predisposing to BN, whereas they seem to predispose bulimic individuals to nutritional impairment and increased harm avoidance.