Circadian rhythms and meal timing: impact on energy balance and body weight

•Energy expenditure, substrate oxidation, and appetite follow circadian rhythms.•Mistimed eating and sleeping disrupt circadian rhythms, increasing risk of obesity.•Shift workers experience severe chronic circadian misalignment.•Social and eating jetlag, variable sleep/eating, cause milder circadian disruption.•Personalization of mealtimes could reduce circadian misalignment and improve health. Energy metabolism and appetite regulating hormones follow circadian rhythms which, when disrupted, could lead to adverse metabolic consequences. Such circadian misalignment, a mismatch between endogenous circadian rhythms and behavior, is most severely experienced by shift workers, due to nighttime wake, daytime sleep, and eating at night. However, circadian misalignment is not restricted to shift workers; milder shifts in sleep and mealtimes, termed social and eating jetlag, are highly prevalent in the general population. Social and eating jetlag result in later mealtimes, which may promote positive energy balance and weight gain. Earlier meal timing, specific to individual endogenous circadian patterns, could serve to reduce cardiometabolic disease burden and aid in weight loss and interventions should be done to test this.