Sedentary time, physical activity, and adiposity in a longitudinal cohort of nonobese young adults

Abstract

Background: Young adulthood is a critical period for excessive weight gain. The extent to which young adults' sedentary time (ST) and moderate-to-vigorous physical activity (MVPA) relate to adiposity and weight gain remains unclear. Objective: The purpose of this study was to examine the relation of ST and MVPA with adiposity and change in adiposity in healthy, nonobese young adults over a 2-y period. Design: Participants were 71 adults aged 20-35 y. Measurements included ST and MVPA by accelerometry and reported energy intake at baseline, and anthropometry (%FM) and fat mass (FM) by dual-energy X-ray absorptiometry at baseline, year 1, and year 2. Associations of baseline ST and MVPA with adiposity were examined with the use of repeated-measures linear regression models, controlling for age, sex, and reported energy intake. The Benjamini-Hochberg procedure was used to adjust for multiple comparisons. Results: Participants [mean ± SD body mass index (BMI; kg/m2): 22.6 ± 2.4] engaged in 8.5 ± 1.5 h ST/d and 0.4 ± 0.3 h MVPA/d. At baseline, adults who engaged in ST for ≥8 h/d had higher FM, %FM, and lower MVPA, whereas those who engaged in MVPA for ≥30 min/d had lower FM and %FM. In fully adjusted models, ST was significantly associated with baseline body weight, hip circumference, BMI, FM, and %FM and with year-1 body weight, waist and hip circumference, FM, and %FM, but not with any year-2 adiposity indicators. MVPA was not significantly associated with any adiposity indicators at baseline, year 1, or year 2 in fully adjusted models. Over 2 y, participants significantly increased waist circumference, BMI, FM, and %FM (all P-values <0.05), but there were no associations among baseline ST and MVPA with change in adiposity. Conclusions: Among nonobese young adults, high ST and low MVPA were related to elevated adiposity but did not predict change in adiposity over time.