Social jet lag (SJL) refers to the discrepancy between average sleep timing on workdays and free days and has been implicated in weight gain, changes in body composition, and chronotype. This study aimed to examine the association between SJL, body composition parameters, and chronotype. Participants wore an actigraph for 14 consecutive days and completed a socioeconomic questionnaire and the Morningness-Eveningness Questionnaire (MEQ). Body composition was assessed by bioelectrical impedance analysis. SJL was calculated as the absolute difference between the midpoint of sleep on weekends and weekdays |SJL = MSweekend - Msweekday|. Data normality was assessed using the Kolmogorov-Smirnov test, and appropriate parametric or nonparametric tests were applied. Adjusted binary logistic regression models were performed with SJL category (low versus moderate/high) as the dependent variable to investigate associations with body composition and chronotype, adjusting for age, sex, and paid employment. The sample comprised 97 individuals, predominantly female (71.1%). Most participants exhibited low SJL (58.8%) and a morning chronotype (57.3%). In the adjusted analyses, which included 91 participants for body composition variables and 96 for chronotype, participants classified as having increased metabolic risk according to waist-to-hip ratio showed higher odds of moderate/high SJL (OR = 5.86, 95% CI: 1.49-22.99). No clear associations were observed for fat mass, fat-free mass, body fat percentage, BMI, or chronotype. These findings indicate that SJL was associated with waist-to-hip ratio classification in this sample, whereas associations with other body composition parameters and chronotype were not evident.
