Relationship between Circadian Rhythms, Feeding, and Obesity

Nearly all living organisms demonstrate circadian rhythms. Although the properties of circadian oscillators have been known for decades, the role of circadian rhythms in weight regulation and metabolism has only recently begun to be studied. Experimental studies have demonstrated that disruption of circadian rhythms through misalignment of the sleep-wake cycle, inappropriately timed light, activity, or feeding have been linked to changes in sleep, dietary behavior, and weight. This chapter will review the experimental literature in animal models and the experimental and observational human literature linking circadian rhythms of sleep and eating to weight regulation. We will begin with a description of circadian rhythms in humans, including the rhythm of the sleep-wake cycle, hunger, and appetite. The second section will review links between circadian disruption (e.g., CLOCK gene mutations in animals, light exposure, chronotype, and social jet lag) and obesity risk. The third section will review the evidence linking the timing of eating to circadian disruption and weight regulation. Overall, the literature suggests that circadian rhythms are important to weight regulation and metabolism. Suggested mechanisms include dietary behavior, appetite stimulating hormones, and glucose metabolism.