Interactions between leptin, neuropeptide-Y and insulin with chronic diurnal fasting during Ramadan.

BACKGROUND: Fasting during the month of Ramadan for Muslims is a unique metabolic model that includes abstinence from food and fluid intake during the period from dawn to sunset as well as a reduction in meal frequency and alterations in the sleep-wakefulness cycle. Leptin, neuropeptide-Y and insulin are thought to play an important role in long-term regulation of caloric intake and energy expenditure. However, the long-term changes and interactions between these factors during this pattern of fasting are not known. SUBJECTS AND METHODS: The study was conducted on 46 healthy female volunteers (age, 22+/-2 years; BMI, 25.3+/-0.7 kg/m2). Anthropometrical measurements, estimation of body fat and fasting serum levels of neuropeptide Y, leptin, insulin and glucose were estimated at baseline (day 1), days 14 and 28 of the month of Ramadan and 2 weeks after Ramadan. RESULTS: Baseline serum levels of leptin correlated positively with body fat (r=0.87, P=0.0002). Serum leptin levels exhibited a significant increase by approximately 41% and neuropeptide-Y levels were decreased by 30.4% throughout the month of Ramadan. In addition, a significant correlation (r=0.63, P=0.0001) was found between changes in serum leptin and serum insulin. However, changes in serum neuropeptide-Y levels did not correlate with those of leptin or insulin CONCLUSIONS: Long-term fasting with interrupted nocturnal eating is associated with significant elevations in serum leptin and insulin and reduction in serum neuropeptide-Y. The changes in serum leptin are likely mediated through insulin. However, changes in neuropeptide-Y appears to be mediated independently of leptin or insulin during this type of fasting

Serum leptin and insulin levels during chronic diurnal fasting.

Ramadan fasting is a unique model that is associated with restriction of the timing of food and fluid intake food from dawn to sunset and reduction in meal frequency and sleep duration. Leptin levels are thought to play a role in long-term regulation of caloric intake and fat deposition. However, the long-term changes in leptin levels during this pattern of fasting are not known. The study was conducted on lean (N=6, BMI=22.5+/-0.4) and obese (N=18, BMI=33.1+/-1.0) healthy female volunteers. Fasting serum levels of leptin, insulin and glucose were estimated at baseline (day 1), days 14 and 28 of the month of Ramadan and 2 weeks after Ramadan. Baseline serum levels of leptin were significantly higher in obese (13.5+/-1.96 microg/L,P<0.05) compared with lean subjects (9.60+/-0.80 microg/L) and correlated positively with body fat (r=0.82, P=0.0004). Serum leptin levels exhibited a significant and comparable increase by 39% and 37% throughout the month in lean and obese subjects, respectively. In addition, a significant correlation (r=0.52, P=0.003) was found between changes in serum leptin and serum insulin levels. We conclude that chronic diurnal fasting is associated with significant elevations in serum leptin. These elevations appear to be mediated by changes in serum levels of insulin. These data support the role of insulin in the long-term regulation of leptin secretion during chronic diurnal fasting followed by nocturnal eating during the month of Ramadan.