Energy Balance and Control of Body Weight: Possible Effects of Meal Timing and Circadian Rhythm Dysregulation

Abstract

Conservation of the energy equilibrium can be considered a dynamic process and variations of one component (energy intake or energy expenditure) cause biological and/or behavioral compensatory changes in the other part of the system. The interplay between energy demand and caloric intake appears designed to guarantee an adequate food supply in variable life contexts. The circadian rhythm plays a major role in systemic homeostasis by acting as "timekeeper" of the human body, under the control of central and peripheral clocks that regulate many physiological functions such as sleep, hunger and body temperature. Clock-associated biological processes anticipate the daily demands imposed by the environment, being synchronized under ideal physiologic conditions. Factors that interfere with the expected demand, including daily distribution of macronutrients, physical activity and light exposure, may disrupt the physiologic harmony between predicted and actual behavior. Such a desynchronization may favor the development of a wide range of disease-related processes, including obesity and its comorbidities. Evidence has been provided that the main components of 24-h EE may be affected by disruption of the circadian rhythm. The sleep pattern, meal timing and meal composition could mediate these effects. An increased understanding of the crosstalk between disruption of the circadian rhythm and energy balance may shed light on the pathophysiologic mechanisms underlying weight gain, which may eventually lead to design effective strategies to fight the obesity pandemic.

Keywords: chronodisruption; energy expenditure; food intake; thermic effect of food.

Figure 1

Energy balance and the adipose organ. Disequilibrium in energy balance regulation can be caused by several factors such as caloric restriction, dietary overfeeding, different macronutrient compositions and several environmental perturbing factors, including those causing chronodisruption. The adipose tissue plays an active role in the regulation of energy balance, not only as a site for lipid storage but also being involved in heat generation (in brown adipose tissue) and adipokine secretion. The adipose organ serves as a dynamic energy depot that constantly conveys signals to the central nervous system to communicate the amount of energy stores and to elicit compensatory responses.

Figure 2

Human circadian rhythm: link between circadian clocks and environmental factors. The central clock and peripheral clocks regulate many physiological functions such as sleep, hunger and control of body temperature. Factors that interfere with the expected demand, including macronutrient composition, meal timing, physical activity and light exposure, may disrupt the physiological harmony between predicted and actual behavior. Such a desynchronization may favor the development of obesity and its complications.