Association of Individuals’ Chronotypes With Obesity and Body Composition in Tehrani Adults in 2020

Objective: Individual’s preferences in time for sleeping, waking up, doing physical and mental activity is dependent on chronotypes. According to these preferences, individuals are categorized to morningness, intermediate, and eveningness chronotype. Recently, it has been suggested that chronotypes are involved in regulation of sleep, appetite, and some metabolic factors. The aim of this study was to investigate the association between chronotypes, obesity, body fat, and lean mass in Tehrani adults.Methods: It was a cross-sectional study on 353 adults aged 18–60 years who referred to Tehran community centers. After anthropometric measurements and collecting data on general information, choronotype, physical activity and 3-day food recalls, fat mass, and lean mass were measured using the method of bioelectrical impedance analysis. SPSS 21 was used to statistical analysis.Results: Of total 353 participants, 11%, 47.6%, and 41.4% had eveningness, intermediate, and morningness chronotypes, respectively. The mean age of individuals with morningness and intermediate was higher than those with eveningness. The prevalence of eveningness in men was higher than in women (p=0.001). Fat mass and lean mass in individuals with eveningness type were higher and lower than those with morningness, respectively (p<0.05). Body mass index and waist circumference showed no significant difference among chronotypes.Conclusion: Eveningness type is associated with increase in fat mass and decrease in lean mass. The effects of chronotype on body fat and lean mass are independent of obesity.