When should I eat: A circadian view on food intake and metabolic regulation.

The circadian clock is a hierarchical timing system regulating most physiological and behavioral functions with a period of approximately 24 h in humans and other mammalian species. The circadian clock drives daily eating rhythms that, in turn, reinforce the circadian clock network itself to anticipate and orchestrate metabolic responses to food intake. Eating is tightly interconnected with the circadian clock and recent evidence shows that the timing of meals is crucial for the control of appetite and metabolic regulation. Obesity results from combined long-term dysregulation in food intake (homeostatic and hedonic circuits), energy expenditure, and energy storage. Increasing evidence supports that the loss of synchrony of daily rhythms significantly impairs metabolic homeostasis and is associated with obesity. This review presents an overview of mechanisms regulating food intake (homeostatic/hedonic) and focuses on the crucial role of the circadian clock on the metabolic response to eating, thus providing a fundamental research axis to maintain a healthy eating behavior.