Plasma leptin response to acute fasting and refeeding in untreated women with bulimia nervosa

Leptin is known to regulate body weight, energy balance, and reproduction. Therefore, investigation of its physiology is of obvious interest in bulimi a nervosa (BN), an eating disorder characterized by body weight-related psy chopathology, acute changes in the energy balance, and reproductive alterat ions. To date, the few studies that have assessed leptin production in BN h ave had several limitations, including the measurement of blood leptin leve ls in treated patients and the lack of normal weight healthy controls, so t hat the information they provide is not conclusive. As the investigation of leptin dynamics is likely to be more informative, we decided to assess lep tin response to acute fasting and refeeding in both untreated patients with BN and healthy controls. Twelve women meeting the diagnostic criteria for BN of the Diagnostic and S tatistical Manual of Mental Disorders, and 10 healthy women of the same age range participated in a 3-day study. At 1800 h on day 1, they received a m eal of 1088 Gal, with 53% carbohydrates, 17% protein, and 30% fat. Then, th ey fasted until 1800 h on day 2, when they received the same meal. On day 3 , they received a standard hospital diet of 2600 Gal, divided into 3 meals, with the same percentages of nutrients as described above. Blood samples w ere collected at different time points for plasma leptin, glucose, and insu lin measurements. In bulimic patients, plasma leptin values were significantly lower than in healthy women (P < 0.0001) and were positively related to body weight, expr essed as body mass index (r = 0.86; P < 0.0001). The leptin response to the fasting/refeeding paradigm significantly differed between patients and con trols (time x group interaction, P < 0.0001). In fact, in healthy subjects, acute fasting induced a 58% decline in the plasma leptin concentration, wh ereas such a decrease was only 7% in bulimic women (P < 0.001). After acute refeeding, plasma leptin increased in both groups, although in the patient s it did not reach the absolute values observed in normal controls. No sign ificant difference was observed between bulimics and controls in plasma ins ulin response to the fasting/refeeding paradigm, whereas an abnormal increa se in blood glucose levels was observed in the patients after the first mea l following acute fasting. We conclude that in untreated women with BN, leptin, despite its very low p lasma values, still holds its function as a sensor of body weight changes, but loses its role of signaling acute changes in energy balance.