OBJECTIVE: To investigate the short- and long-term effects of dietary restriction on serum leptin in obese women and the role of the gastrointestinal system in the short-term regulation of leptin production. DESIGN: Clinical longitudinal study of anthropometric and serum leptin changes induced in obese women by a balanced 300 kcal/d very low calorie diet (VLCD), administered either orally or parenterally for 5 d, and by a balanced 900 kcal/d low calorie diet (LCD) lasting six months. SUBJECTS: 20 obese women (age: 38.1±12.7 y; body mass index (BMI): 40.2±8.3 kg/m2). RESULTS: Five days following VLCD, a modest, even if significant (P<0.0001), fall of both body weight (BW) and BMI was observed, along with a dramatic (>50%) highly significant (P<0.0001) reduction of circulating serum leptin. Baseline and five-day anthropometric and biochemical findings were closely similar in the group of orally fed subjects, when compared with those of their parenterally fed counterparts. The baseline positive correlation between serum leptin and BMI ( =0.533) increased (P<0.05) at the end of the five day VLCD (=0.849). A further fall of BW and BMI was observed at day 30 (P<0.001) and day 180 (P<0.01) during the 900 kcal/d LCD, while the serum leptin concentration gradually increased until day 180 when it was only slightly but non significantly lower than at baseline. At the end of the study, the correlation between serum leptin and BMI was similar to the baseline (=0.562). CONCLUSIONS: Energy restriction causes a fall of serum leptin apparently not mediated by gastrointestinal signals and it seems not to affect the long-term regulatory pathways of circulating leptin. | 
