Fig. 8. Conceptual scheme for meal timing effects on internal circadian alignment and glucose tolerance.

In the NMC group (left), there is a misalignment of the fasting/eating cycle (i.e., night eating) and the sleep/wake cycle (i.e., night work) with the central circadian rhythm. This scenario results in (1) internal circadian misalignment across circadian oscillators (illustrated by hypothesized out-of-phase clocks) and with the misalignment of circadian peripheral rhythms (e.g., endogenous circadian glucose and insulin rhythms) relative to the central circadian rhythm (e.g., endogenous circadian CBT rhythm). It also results in (2) impaired glucose tolerance, predicted to occur because of decreased insulin release and insulin sensitivity, thereby causing dysglycemia. In contrast, the DMI group (right) maintains the alignment of the fasting/eating cycle (i.e., day eating) with the central circadian rhythm, despite the misalignment of the sleep/wake cycle (i.e., night work). Consequently, this leads to (1) internal circadian alignment and (2) normalized glucose tolerance. This state of normoglycemia may prevent glucose intolerance in individuals experiencing circadian rhythm disruption, as in the case of night workers.