Role of the Synchronization of Circadian Clock by Meal-Timing in Obesity and Type 2 Diabetes

Abstract

Obesity and diabetes are increasing worldwide in epidemic proportion. Most alarmingly, is that in the last three decades, no country has successfully succeeded in reducing obesity and diabetes rates, therefore "unless the strategies for combating this epidemic are changed," both obesity and diabetes will increase exponentially in the years to come. Most of the metabolic processes involved in glucose and energy metabolism, i.e., β-cell secretory function, insulin sensitivity, muscular glucose uptake, and hepatic glucose production, display daily oscillation and are controlled by the circadian clock, to anticipate the recurring feeding-fasting cycles and to optimize metabolic efficiency in the appropriate temporal sequence. Growing evidence shows that meal timing not aligned with the light/dark cycle, like skipping breakfast, overeating at night, or snacking all day, including at hours assigned to sleep, lead to asynchrony and disruption of circadian clock gene expression and metabolic and appetite disturbances. It has been suggested, that the circadian misalignment and mistimed meals, typical of the modern society exposed to a 7/24 activity schedule, is the underlying cause of the vertiginous rise of obesity and T2D. This review will focus on the recent studies reporting that meal timing aligned with the circadian clock, by shifting most calories and carbohydrates to the early hours of the day, through resetting the synchrony of the circadian clock gene expression, may improve glucose and energy metabolism and appetite regulation, resulting in more efficient weight loss, better glycemic control and reduced appetite, thereby preventing obesity and hyperglycemic relapse.