Associations of physical activity and sedentary time with body composition in Brazilian young adults

Abstract

The findings of studies on the association between physical activity and adiposity are not consistent, and most are cross-sectional and used only self-reported measures. The aims of this study were to evaluate: 1) independent and combined cross-sectional associations of objectively-measured physical activity and sedentary time with body composition outcomes at 30 years, and 2) prospective associations of changes in self-reported physical activity from 23 to 30 years with the same outcomes in participants from the 1982 Pelotas (Brazil) Birth Cohort. Body mass index, waist circumference, visceral abdominal fat, fat mass index, and android/gynoid fat ratio were the outcomes. 3,206 participants were analysed. In cross-sectional analyses, higher objectively-measured moderate-to-vigorous physical activity was associated with lower body mass index (β = 0.017, 95%CI: -0.026; -0.009), waist circumference (β = -0.043, 95%CI: -0.061; -0.025), visceral abdominal fat (β = -0.006, 95%CI: -0.009; -0.003), and fat mass index (β = -0.015, 95%CI: -0.021; -0.009), independent of sedentary time. Sedentary time was independently associated only with higher fat mass index (β = 0.003, 95%CI: 0.001; 0.005). In longitudinal analyses, using self-reported measure, adiposity was lower among those who were consistently active or who became active. Adiposity was similar among the "became inactive" and "consistently inactive" subjects. Our findings suggest metabolic benefits from engagement in physical activity throughout young adulthood, with stronger associations on concurrent levels.

Figure 1

Flow diagram of study participants. *Number of participants who had available information on self-reported physical activity at 23 and 30 years of age and on at least one of the body composition outcomes.

Figure 2

Adjusted means (95%CI) of anthropometric and body composition outcomes by combined categories of moderate-to-vigorous physical activity and sedentary time at 30 years of age. Adjusted for sex, skin colour, family income at birth, maternal schooling at birth, birth weight, socioeconomic status at 30 years, schooling at 30 years, smoking at 30 years, and daily energy intake at 30 years. MVPA: moderate-to-vigorous physical activity; SED: sedentary time. Socioeconomic status at 30 years is the covariate with more missing data. N of the analyses from the top to the bottom of the figure: 2,145; 2,153; 2,121; 2,072; 2,083.