The association among circadian rhythm, circadian genes and chrononutrition, its effect on obesity: a review of current evidence

Circadian rhythms, also known as circadian clocks, are cyclic endogenous biological patterns of an approximately 24-hour cycle which regulate the timing of physiology, metabolism, and behavior. Recent research in the field of circadian science has suggested that the timing of food intake may also play a role in markers of health, in addition to food choice and food quantity. There is emerging evidence suggesting that the timing of dietary intake, so-called chrono-nutrition, may be influenced by an individuals chronotype. For example, the evening type has been linked to unhealthy diet, which could indicate a higher possibility of obesity. On the other hand, the continuum of chronotype diversity is largely mediated by genes. The presence of single nucleotide polymorphisms (SNP) of clock genes have been associated with obesity, chronotype, metabolic disturbances, and dietary habits (e.g., breakfast skipping, meal timing, energy/macronutrient intake). In this review, we outline the current knowledge of the interactions between clock genes, chronotype, dietary intake and chrono-nutrition.Additionally, it is emphasized that the COVID-19 pandemichas had a significant impact on the circadian system, dietary choices and meal timing. For this reason, the current review aims to focus on how chronotype/sleep and chrono-nutrition are affected during the COVID-19 pandemic.