The relationships between indicators of physical activity, indicators of sedentary behaviour and adiposity in French adults: the FLVS II study

Increasing habitual physical activity and decreasing sedentary behaviour have both been identified as targets for the prevention of unhealthy weight gain and obesity. To improve health monitoring in the context of nutrition-related disease prevention, there is a need to better define relevant indicators of sedentary behaviour. The aim of this study was to investigate the relationships between indicators of physical activity, indicators of sedentary behaviour and body fat in French adults. We analysed cross-sectional data from a community-based survey in northern France (213 men, age: 44±5 years; 192 women, age: 42±4 years; mean±SD). Physical activity and sedentary behaviour during the past year were assessed using the Modifiable Activity Questionnaire. Indicators of physical activity were leisure-time and occupational physical activity, indicators of sedentary behaviour during leisure were reading and “screen viewing” (including time spent watching television/video, playing video games, and using a computer). Body-fat percentage was assessed using bio-impedance analysis. In univariate analysis (Spearman rank correlations), reading and screen viewing were not significantly correlated; reading was positively associated with leisure-time physical activity in women and negatively associated with occupational physical activity in men. In multivariate analyses (stepforward regression models) stratified by gender and educational level, independent predictors of percent body fat included, in women, screen viewing (positive association), occupational physical activity (positive association) and leisure-time activity (negative association), but not reading; in men, only reading was associated with percent body fat, with a negative relationship in those with a high educational level. Relationships between indicators of sedentary lifestyle and body fat differ according to gender and type of sedentary pasttime. The data emphasise that sedentary lifestyle represents a complex set of behaviours and that various sedentary behviours may have distinct effects with regard to health outcomes. These results point out the need to assess selected indicators of sedentary behaviour when considering health monitoring in public health nutrition.