The influence of intermittent fasting on the circadian pattern of melatonin while controlling for caloric intake, energy expenditure, light exposure, and sleep schedules: A preliminary report

Abstract

AIMS:We hypothesized that if we control for food composition, caloric intake, light exposure, sleep schedule, and exercise, intermittent fasting would not influence the circadian pattern of melatonin. Therefore, we designed this study to assess the effect of intermittent fasting on the circadian pattern of melatonin.METHODS:Eight healthy volunteers with a mean age of 26.6 ± 4.9 years and body mass index of 23.7 ± 3.5 kg/m2 reported to the Sleep Disorders Center (the laboratory) on four occasions: (1) adaptation, (2) 4 weeks before Ramadan while performing Islamic intermittent fasting for 1 week (fasting outside Ramadan [FOR]), (3) 1 week before Ramadan (nonfasting baseline [BL]), and (4) during the 2nd week of Ramadan while fasting (Ramadan). The plasma levels of melatonin were measured using enzyme-linked immunoassays at 22:00, 02:00, 04:00, 06:00, and 11:00 h. The light exposure, meal composition, energy expenditure, and sleep schedules remained the same while the participants stayed at the laboratory.RESULTS:The melatonin levels followed the same circadian pattern during the three monitoring periods (BL, FOR, and Ramadan). The peak melatonin level was at 02:00 h and the trough level was at 11:00 h in all studied periods. Lower melatonin levels at 22:00 h were found during fasting compared to BL. Cosinor analysis revealed no significant changes in the acrophase of melatonin levels.CONCLUSIONS:In this preliminary report, under controlled conditions of light exposure, meal composition, energy expenditure, and sleep-wake schedules, intermittent fasting has no significant influence on the circadian pattern of melatonin.

How does diurnal intermittent fasting impact sleep, daytime sleepiness, and markers of the biological clock? Current insights

“…Studies that assessed changes in core body temperature during Ramadan diurnal IF have reported conflicting results (Table 1). In general, studies that assessed the circadian rhythm during Ramadan diurnal intermittent fasting can be divided into two categories: category 1 encompasses studies that examined the changes in some markers of the circadian clock in an unconstrained “free-living environment” without controlling for confounders and lifestyle changes such as meal composition, caloric intake, total sleep time, energy expenditure, or light exposure,24–27 and category 2 encompasses studies that controlled for the above confounders 28–30…”

“…None of the above studies accounted for potential confounders that may accompany Ramadan and affect the measured melatonin levels. In a subsequent study, we attempted to overcome those limitations by assessing circadian profiles of serum melatonin during diurnal IF outside Ramadan (to assess the impact of diurnal IF act in the absence of the lifestyle changes associated with Ramadan) and during the second week of Ramadan while controlling for light exposure, sleep pattern, total sleep time, and meal composition 28. In eight healthy volunteers, serum melatonin was measured at five time points (22:00, 02:00, 04:00, 06:00, and 11:00) three times: 4 weeks before Ramadan where volunteers were asked to perform diurnal IF (fasting outside the month of Ramadan) for 1 week, 1 week before Ramadan during which volunteers were not fasting and living a routine life, and during the second week of Ramadan while performing diurnal IF.…”

The effects of diurnal intermittent fasting on the wake-promoting neurotransmitter orexin-A

“…For details about study design, we refer the reader to previous studies assessing neurohormonal changes during Ramadan. [ 8 24 ]…”

“…We used the same intermittent fasting protocol described in previous studies. [ 8 23 24 ] During the fasting periods (FOR and Ramadan), the participants were asked to fast from dawn to sunset.…”

Recent Evidence on the Impact of Ramadan Diurnal Intermittent Fasting, Mealtime, and Circadian Rhythm on Cardiometabolic Risk: A Review

“…Reviewing all studies that aimed to assess the circadian rhythm changes during Ramadan reveals two types of studies: (1) studies that were conducted in a non-constrained environment and did not control for lifestyle changes, caloric intake, and nocturnal meal timings, and these studies reported rapid and significant delays in bedtime and rising time (45)(46)(47); and (2) recent studies that accounted for sleep/wake schedule, sleep duration, light exposure, caloric consumption, meal timings and energy expenditure, which demonstrated no changes in circadian rhythm during fasting (48)(49)(50). In the second group, meals were served early at night, the participants slept early according to their usual routine and then woke up for the predawn meal in the early morning.…”