Altered circadian energy metabolism and chronobiological risk factors of chronic diseases

Franz Halberg is regarded by many worldwide as the father of chronobiology, the science of objectively quantifying and investigating mechanisms of biologic time structure, including rhythmic manifestations of life. Most variables in most organisms are circadian periodic. An organism’s response to external stimuli, such as a single daily meal, also changes predictably in a circadian stage-dependent manner. Both the feeding schedule and the lighting regimen act as major synchronizers of the circadian system. This chapter reviews how caloric restriction and time-restricted feeding affect circadian rhythms and how circadian disruption is associated with metabolic disorders. While a heightened disease risk and overt disease tend to be associated with a weakening of circadian rhythms, reflected by reduced amplitude and/or phase desynchronization, interventions such as caloric restriction that prolong health span are usually associated with robust and stable large-amplitude circadian variation. Much work at the molecular and cellular levels has shed light on how circadian clocks are tightly coupled to cellular metabolism as they share a number of nutrient-sensing pathways, some of which are also briefly reviewed herein. Time-restricted feeding emerges as a nonpharmacologic lifestyle option available to increase metabolism and reduce body weight, warranting further investigation in relation to metabolic disorders such as obesity and type 2 diabetes.