Insufficient sleep and circadian misalignment are both stressors to metabolic health and are linked to adverse health outcomes, according to the authors of a study published in Nature Reviews Endocrinology. This predisposition, which can promote weight gain, has received more attention from researchers in the past decade.
The current study examines the role of insufficient sleep and circadian misalignment in obesity and the association of metabolic dysregulation. Further, the authors evaluate common sleep disruptors and discuss the effects of insufficient sleep and circadian misalignment on appetite hormones (focusing on ghrelin, leptin, and peptide-YY), energy expenditure, food intake and choice, and obesity risk. The impact of obesity on sleep is also taken into consideration, as well as potential strategies to minimize the adverse effects of sleep and circadian disruption on metabolic health.
The study authors note that sleep patterns have changed, with sleep disruptors (or sleep stealers) growing in number and complexity due to cultural and societal changes. Additionally, different sleep patterns, such as biphasic and multiphasic sleep, were previously reported in history, with these patterns characterized by a first sleep that occurs between 9pm and 1am, and a second sleep from the end of the first sleep until sunrise. Several disruptors hindering sleep include modern working patterns, the amount of screen time and when electronics are used, sleep-disrupting substances (eg, smoking and alcohol), and emotional stressors.
According to the authors, the 24-hour patterns of energy expenditure are more relevant to understanding weight gain and metabolic dysregulation, compared to fasting values. The 24-hour pattern—which is measured under controlled energy intake, controlled activity, and bed rest conditions—demonstrates that increases in energy expenditure occur in response to meals. Further, they noted that sleep influences a drop in energy expenditure that is absent when wakefulness is maintained.
Staying awake for 1 night results in an approximate 7% increase in 24-hour energy expenditure in healthy young adults; however, activity or diet-induced energy expenditure that occur overnight results in energy expenditure during sleep deprivation higher than 7%. Insufficient sleep increases 24-hour energy expenditure by approximately 100 kcal per day; however, it also increases energy intake by greater than 250kcal per day, resulting in a positive energy balance and weight gain. Further, sleep restriction increases the urge to consume food, and the excess intake, which is related to cognitive control and reward mechanisms than to appetite hormones.
From a metabolic perspective, circadian misalignment is defined as the energy intake, activity, and wakefulness that occur during the biological night. Circadian misalignment reduces 24-hour energy expenditure by approximately 3%, or 55 kcal per day, and changes the levels of appetite hormones, promoting unhealthier food choices than conditions of adequate sleep.
The authors note that prior research on circadian misalignment and obesity risk has largely focused on fairly large challenges to the circadian system, such as working a night shift or a 12-hour inverted shift in behaviors. According to the authors, smaller degrees of misalignment (eg, staying up late on a weekend, travel, early work start times) that occur more frequently than large degrees of misalignment, and show associations with adverse metabolic health.
According to the study authors, people with obesity typically report reductions in sleep duration and sleep quality; however, prior research largely focused on sleep disorders, therefore, little is known about the independent effects of obesity on sleep. Further, most of these investigations rely on self-reported data from participants resulting in inadequate control for researchers. Prior studies suggest that compared to adults without obesity who reported between 7 and 8 hours per night, those with obesity are more likely to report short or long sleep durations. Additionally, adults with obesity but without sleep apnea reported excessive daytime sleepiness. Further, behavioral factors (eg, poor diet, lack of physical activity) are likely to impact sleep.
The study authors identify a variety of methods that were effective in improving sleep across prior studies, including physical activity, eating healthily, avoiding eating at night, reducing exposure of blue light at night, avoiding caffeine late in the day, limiting alcohol consumption and avoiding smoking, and taking short naps during the day (up to 40 minutes).
Evidence suggests that insufficient sleep and circadian misalignment can contribute to adverse metabolic health and obesity by altering multiple factors of energy metabolism and behavior. Circadian misalignment increases the risk of obesity by reducing the individual’s 24-hour energy expenditure. Further, changes in appetite hormones stimulate hunger and energy intake. The findings indicate that even without changes in energy intake, weight gain can result if energy is consumed at the incorrect circadian times. Although investigations within this subject have increased, a gap remains. The study authors urge further research to address missing information.
Chaput JP, McHill AW, Cox RC, et al. The role of insufficient sleep and circadian misalignment in obesity. Nat Rev Endocrinol. 2023;19(2):82-97. doi:10.1038/s41574-022-00747-7