Effects of dietary restriction on serum leptin concentration in obese women

OBJECTIVE: To investigate the short- and long-term effects of dietary restr iction 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 chan ges 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 balance d 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/m(2)). RESULTS: Five days following VLCD, a modest, even if significant (P < 0.000 1), fall of both body weight (BW) and BMI was observed, along with a dramat ic (> 50%) highly significant (P < 0.0001) reduction of circulating serum l eptin. Baseline and five-day anthropometric and biochemical findings were c losely similar in the group of orally fed subjects, when compared with thos e of their parenterally fed counterparts. The baseline positive correlation between serum leptin and BMI (rho = 0.533) increased (P < 0.05) at the end of the five day VLCD (rho = 0.849). A further fall of BW and BMI was obser ved 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 whe n 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 (rho = 0.562). CONCLUSIONS: Energy restriction causes a fall of serum leptin apparently no t mediated by gastrointestinal signals and it seems not to affect the long- term regulatory pathways of circulating leptin.