Carbohydrate intake and circadian synchronicity in the regulation of glucose homeostasis

PURPOSE OF REVIEW: Glucose metabolism is under circadian regulation, with insulin secretion and sensitivity being highest in the morning as compared to the evening. The present review will discuss the existing evidence for the role of meal and macronutrient timing to improve glucose metabolism and reset circadian clocks, with a focus on the evidence in humans. RECENT FINDINGS: Shortening the daily eating window (also known as time-restricted eating), or skewing food intake towards breakfast and away from the evening meal both improve glucose control in people with impaired glucose metabolism. Insulin is recently purported to be a zeitgeber and thus an important reset signal for peripheral circadian clocks in vitro and in mice. Although few studies have tested the impact of macronutrient timing in humans, eating a greater proportion of carbohydrates earlier, rather than later, in the day is associated with better glucose control. SUMMARY: The impact of carbohydrate intake timing on endogenous central and peripheral clocks, and its potential to optimize circadian regulation and improve glycaemic control, are not well understood but are currently under intense exploration.