0260 Chronotype is not Associated with 12-Month Changes in Body Composition or Anthropometrics in Black Emerging Adults: SHOW Study Preliminary Findings

Abstract Introduction Having a late type vs. early chronotype has been associated with a higher risk of weight gain and obesity. Black emerging adults (ages 18-28 years) have a greater risk of obesity, yet there is little research examining relationships between chronotype and long-term changes in body weight and body composition in this population. These analyses from the Sleep, Health Outcomes, and Body Weight (SHOW) Study examined preliminary associations between chronotype with 6- and 12-month changes in body composition and anthropometrics in a sample of Black emerging adults. Methods The SHOW study aims to recruit 150 Black emerging adults and assess changes in body weight and composition from baseline (BLN) to 6-months (6MO), and 12-months (12MO). Chronotype was measured at BLN with the Morningness-Eveningness Questionnaire (MEQ) and analyzed as a continuous variable (possible score, 16-86; higher scores indicate an earlier chronotype). Body composition (fat mass index and fat-free mass index (kg/m2); DXA or Bod Pod) and anthropometrics (body weight, waist and hip circumferences) were measured during an in-laboratory visit at each timepoint. Partial Pearson correlations examined associations between chronotype with 6- and 12-month changes in body composition and anthropometrics, controlling for BLN body weight. Given the exploratory nature of these analyses, we investigated these associations in the entire sample and in males and females separately. Results To date, 6MO data are available in 68 participants (46 females; BLN: age, 20.3±2.0 yrs; body mass index, 26.1±6.2 kg/m2; fat mass index, 7.7±5.2 kg/m2; fat-free mass index, 17.1±3.0 kg/m2; waist-to-hip ratio, 0.80±0.07 cm; MEQ score, 47.1±6.1), and 12MO data are available in 44 participants (31 females). In the entire sample, MEQ score was not significantly associated with changes in body composition or anthropometric variables. In females, having an earlier chronotype (or higher MEQ score) was associated with a greater 12-month decrease in fat-free mass index (r=-0.37, p=0.050), but this trend was not observed in males (r=0.31, p=0.32). Conclusion These preliminary findings suggest that chronotype is not associated with changes in body weight and body composition in Black emerging adults, although it may impact changes in body composition differently between males and females. Support (if any) NIH Grant R01HL163804