The role of insufficient sleep and circadian misalignment in obesity

Abstract

Traditional risk factors for obesity and the metabolic syndrome, such as excess energy intake and lack of physical activity, cannot fully explain the high prevalence of these conditions. Insufficient sleep and circadian misalignment predispose individuals to poor metabolic health and promote weight gain and have received increased research attention in the past 10 years. Insufficient sleep is defined as sleeping less than recommended for health benefits, whereas circadian misalignment is defined as wakefulness and food intake occurring when the internal circadian system is promoting sleep. This Review discusses the impact of insufficient sleep and circadian misalignment in humans on appetite hormones (focusing on ghrelin, leptin and peptide-YY), energy expenditure, food intake and choice, and risk of obesity. Some potential strategies to reduce the adverse effects of sleep disruption on metabolic health are provided and future research priorities are highlighted. Millions of individuals worldwide do not obtain sufficient sleep for healthy metabolic functions. Furthermore, modern working patterns, lifestyles and technologies are often not conducive to adequate sleep at times when the internal physiological clock is promoting it (for example, late-night screen time, shift work and nocturnal social activities). Efforts are needed to highlight the importance of optimal sleep and circadian health in the maintenance of metabolic health and body weight regulation. Insufficient sleep and circadian misalignment are common in modern society. Insufficient sleep and circadian misalignment are important metabolic stressors and are associated with weight gain and obesity. Insufficient sleep increases energy expenditure by ~100 kcal per day but also increases energy intake by >250 kcal per day, resulting in a positive energy balance and weight gain. Sleep restriction increases the drive to eat, and excess food intake resulting from not sleeping enough is more related to cognitive control and reward mechanisms than to appetite hormones. Circadian misalignment reduces 24-h energy expenditure by ~3% (~55 kcal per day), alters the levels of appetite hormones and promotes unhealthier food choices than conditions of adequate sleep. Insufficient sleep and circadian misalignment contribute to obesity risk. This Review discusses how modern society disrupts sleep, it considers evidence from human studies on how sleep disruption affects energy expenditure, appetite hormones and food intake, and discusses some potential strategies to reduce the adverse effects of sleep disruption.