Meal Timing, Aging, and Metabolic Health

Abstract

A growing body of evidence suggests that meal timing is an important factor for metabolic regulation and that the circadian clock tightly interacts with metabolic functions. The proper functioning of the circadian clock is critical for maintaining metabolic health. Therefore, chrononutrition, a novel discipline which investigates the relation between circadian rhythms, nutrition, and metabolism, has attracted increasing attention in recent years. Circadian rhythms are strongly affected by obesity, type 2 diabetes, and other dietary-induced metabolic diseases. With increasing age, the circadian system also undergoes significant changes which contribute to the dysregulation of metabolic rhythms. Metabolic diseases are a major health concern, particularly in light of a growing aging population, and effective approaches for their prevention and treatment are urgently needed. Recently, animal studies have impressively shown beneficial effects of several dietary patterns (e.g., caloric restriction or time-restricted feeding) on circadian rhythms and metabolic outcomes upon nutritional challenges. Whether these dietary patterns show the same beneficial effects in humans is, however, less well studied. As indicated by recent studies, dietary approaches might represent a promising, attractive, and easy-to-adapt strategy for the prevention and therapy of circadian and metabolic disturbances in humans of different age.

Keywords: aging; chrononutrition; circadian clock; meal timing; metabolic health.

Figure 1

Circadian regulation of metabolism. In mammals, the circadian clock consists of a master clock in the suprachiasmatic nucleus (SCN) of the hypothalamus, which is synchronized by light/dark signals, and peripheral clocks, which is orchestrated by the master clock and controls metabolic rhythms. Food consumption can also entrain the endogenous clock but has a stronger influence on peripheral clocks than on the SCN. Illustrations, used in this Figure, were adapted from Servier Medical Art (http://smart.servier.com/). Servier Medical Art by Servier is licensed under a Creative Commons Attribution 3.0 Unported License.

Figure 2

Scheduled meals as an extra-SCN zeitgeber for the entrainment of circadian rhythms in aging and metabolic diseases. In later life, a reduced sensitivity of the master clock to light, imbalances of neurotransmitters, and desynchronization of SCN neurons lead to a decrease in the overall amplitude of its firing rhythm. In turn, a weaker SCN output signal reduces the strength of downstream oscillators in central and peripheral tissues. In metabolic diseases such as obesity and type 2 diabetes (T2D), circadian rhythms are also reduced or dysregulated. Providing other zeitgebers, such as scheduled meals, which act on the circadian system via extra-SCN pathways, may entrain the circadian system and restore circadian rhythms. Illustrations, used in this Figure, were adapted from Servier Medical Art (http://smart.servier.com/). Servier Medical Art by Servier is licensed under a Creative Commons Attribution 3.0 Unported License.