Diurnal Intermittent Fasting during Ramadan: The Effects on Leptin and Ghrelin Levels

BaHammam AS (2014) Diurnal Intermittent Fasting during Ramadan: The Effects on Leptin and Ghrelin Levels. PLoS ONE 9(3): e92214. doi:10.1371/journal.pone.0092214 Diurnal Intermittent Fasting during Ramadan : The Effects on Leptin and Ghrelin Levels Mohammed A. Alzoghaibi 0 Seithikurippu R. Pandi-Perumal 0 Munir M. Sharif 0 Ahmed S. BaHammam 0 Zane Andrews, Monash University, Australia 0 1 Department of Physiology, College of Medicine, King Saud University , Riyadh , Saudi Arabia , 2 Center for Healthful Behavior Change, Division of Health and Behavior, Department of Population Health, New York University Langone Medical Center, Clinical and Translational Research Institute , New York , New York, United States of America, 3 Somnogen Canada Inc. , Toronto, Ontario , Canada , 4 The University Sleep Disorders Center, Department of Medicine, College of Medicine, King Saud University , Riyadh , Saudi Arabia , 5 National Plan for Science and Technology, King Saud University , Riyadh , Saudi Arabia We aimed to assess the effect of Islamic intermittent fasting, during and outside of Ramadan, on plasma levels of leptin and ghrelin while controlling for several potential confounding variables. Eight healthy male volunteers with a mean age of 26.664.9 years reported to the sleep disorders center (SDC) at King Saud University on four occasions: 1) adaptation; 2) 4 weeks before Ramadan while performing Islamic fasting for 1 week (baseline fasting) (BLF); 3) 1 week before Ramadan (nonfasting baseline) (BL); and 4) during the second week of Ramadan while fasting. Plasma leptin and ghrelin levels were measured using enzyme-linked immunoassays at 22:00, 02:00, 04:00, 06:00, and 11:00. During BLF, there were significant reductions in plasma leptin concentrations at 22:00 and 02:00 compared with the baseline concentrations (at 22:00: 194.26177.2 vs. 146.76174.5; at 02:00: 203.86189.5 vs. 168.16178.1; p,0.05). During Ramadan, there was a significant reduction in plasma leptin levels at 22:00 (194.26177.2 vs. 132.66130.4, p,0.05). No significant difference in plasma ghrelin concentrations was detected during the BL, BLF, or Ramadan periods. Cosinor analyses of leptin and ghrelin plasma levels revealed no significant changes in the acrophases of the hormones during the three periods. The nocturnal reduction in plasma leptin levels during fasting may be the result of the changes in meal times during fasting. - Funding: This study was supported by a grant from the National Plan for Science and Technology, King Saud University, and King Abdulaziz City for Science and Technology, Saudi Arabia (http://npst.ksu.edu.sa/index.php?page_id = 101). However, the funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Ramadan, the ninth month of the Muslim lunar calendar, is a unique model of long-term intermittent fasting. In some Islamic countries, Ramadan is associated with lifestyle changes that include changes in meal frequency and composition, sleep/wake patterns, and sleep duration [1,2]. During Ramadan, Muslims must refrain from eating and drinking from dawn to sunset. Ramadan follows the Islamic (Hijri) year that follows the lunar system, which is shorter than the Gregorian year by 11 days. Thus, Ramadan occurs during a different season every nine years, which significantly influences the durations of day and night. Furthermore, changes occur in the day/night activity patterns during Ramadan, such as late night prayer and the early awakening for the pre-dawn meal (Suhur). Moreover, in some Islamic countries, stores and shopping malls open late and remain open far into the night. Additionally, eating habits may change in some cultures during Ramadan; specifically, people prefer fried foods and consume an excessive amount of sweets [1]. The above patterns indicate that the physiological changes that occur during Ramadan fasting may be different from those that occur during experimental fasting [3]. Leptin, the protein product of the obese gene, is thought to play a role in long-term regulation of caloric intake, fat deposition, and energy balance [4,5]. It acts as a signal to the brain, reflecting energy stores in the body [6]. The circadian rhythm of serum leptin has previously been demonstrated in normal subjects, with peak averages between 22:00 and 03:00 [7,8]. Morning leptin levels were relatively high; however, a dramatic reduction in plasma leptin was noted after breakfast, and the lowest level was between 08:00 and 17:00 [8]. Furthermore, it has been shown that plasma leptin profiles were higher in obese than in lean subjects and higher in women than in men [9]. Moreover, meal time shifting has been shown to entrain the diurnal rhythm of leptin, which indicates that eating may be associated with the nocturnal increase in leptin [10]. Ghrelin is an appetite-stimulating peptide that appears to act as a peripheral orexigen that counteracts the action of leptin [11]. Several studies have shown a competitive interaction between ghrelin and leptin in the regulation of food intake [12,13]. Animal studies have shown that fasting and food intake affect both hormones [14]. In humans, plasma ghrelin levels increase preprandially and decrease after meals [15]. Previous studies have shown that Ramadan fasting may influence the circadian rhythms of several biological variables, including hormones [3]. The long-term changes in plasma leptin levels during intermittent Ramadan fasting have not been extensively studied. Bogdan et al showed a shift in the circadian rhythm of leptin but no significant changes in the mean concentration of plasma leptin levels on the 23rd day of Ramadan daytime fasting in 10 male subjects [16]. By contrast, other studies showed that shortterm fasting results in a 3066% reduction in leptin levels [17]. Prolonged fasting has been shown to increase plasma ghrelin levels in mice and rats [12,18]. However, the changes in ghrelin plasma levels have not been assessed during Ramadan fasting. Several lifestyle changes that occur during Ramadan may influence plasma leptin and ghrelin levels, such as meal time, sleep/wake schedule and sleep duration [19], light exposure [20], and exercise [21]. Previous studies that assessed the levels of leptin during Ramadan fasting did not monitor sleep objectively to document sleep duration and sleep quality, did not account for the possibility that attendant cultural and lifestyle changes that occur during Ramadan, such as delays in starting school and work, increased activity in malls until late at night, and other changes in the day-night activity patterns that may affect the sleep patterns of individuals regardless of fasting. Therefore, this study was designed to assess the effect of intermittent Islamic fasting during and outside of Ramadan on plasma levels of leptin and ghrelin while controlling for the sleep/ wake schedule, sleep duration and quality, meal composition (...truncated)