Association between dietary intake and the expression of clock genes in adults: a brief report

Background The circadian system regulates several physiological processes, including energy metabolism, through the expression of core clock genes. Animal studies suggest that dietary composition can influence circadian gene expression; however, evidence in humans remains limited. Objective This study aimed to explore the association between dietary macronutrient intake and the expression of circadian clock genes in the whole blood of adults with distinct metabolic profiles. Methods Nineteen adults (94.7% female; 43.4 ± 16.05 years) were categorized into healthy-weight and overweight/obesity groups based on BMI. Dietary intake was assessed using a 3-day food diary, and clock gene expression ( CLOCK , BMAL1 , PER2 , CRY ) was evaluated in whole blood samples collected between 08:00 a.m. and 04:00 p.m. Statistical analyses included group comparisons and correlation analyses between macronutrient intake and gene expression. Results No statistically significant differences were observed in the clock gene expression between BMI groups, although group-level trends were noted, particularly in PER2 and CRY expression. The overweight/obesity group exhibited a significantly higher percentage of energy intake from protein. Correlation analyses revealed several time-dependent associations between macronutrient intake and clock gene expression. Notably, in the healthy BMI group, BMAL1 and CRY expression correlated with lipid and protein intake, while in the overweight/obesity group, CLOCK expression was strongly associated with both lipid and carbohydrate intake. Conclusion These findings suggest that macronutrient composition may influence peripheral circadian gene expression in a time- and BMI-dependent manner. Further research is necessary to confirm these associations in larger and more diverse populations and to investigate the potential for chrononutrition strategies to support metabolic health.