Sedentary Behaviour and Subsequent Obesity outcomes in Adults: A Systematic Review and Meta-analysis of Prospective Studies

Background: The modernisation of workplace and leisure environments in Western societies has resulted in people spending more time in sedentary behaviours. Too much sedentary behaviour has been proposed as an important contributing factor to weight gain and to the increase in the prevalence of obesity. However, systematic reviews that have taken a qualitative approach to assessing the observational studies of sedentary behaviour and measures of obesity have found an inconclusive or limited relation. A large body of evidence has been published since the last narrative reviews and a quantitative evaluation of all evidence to date may bring further clarity to understanding the relation between sedentary behaviour and obesity. Objective: The aim of this systematic review was to conduct a meta-analysis of studies that examined the relation between sedentary behaviour and markers of obesity. It was hoped that applying a quantitative approach to updating and extending previous qualitative reviews would help clarify the extent of this relation. Design: This systematic review and meta-analysis follows the preferred guidelines for conducting and reporting meta-analyses. Data sources were English language studies in Ovid MEDLINE (R) 1946 to July 2015, Ovid MEDLINE pending, Ovid Embase Classic + Embase 1947 to July 2015, Ovid AMED 1985 to July 2015 and PUBMED through July 2015, with manual searches of in-text citations. Eligible studies were prospective cohort studies or randomised control trials investigating sedentary behaviour and measures of obesity in adults, adjusted for physical activity. Results: Twenty-five prospective studies were included in the systematic review, 16 of which had comparable outcomes for inclusion in the meta-analysis. The meta-analysis was performed on measures of obesity including body mass index (BMI), body mass, waist circumference and obesity risk. There was no relation between; sedentary behaviour (higher versus lower) and BMI: [0.11 kg/m2 (95%CI, -0.16 to 0.38; P = 0.418)], sedentary behaviour (dose response, 1 h per day) and BMI: [0.04 kg/m2 (95%CI, -0.04 to 0.13; P = 0.292)], sedentary behaviour (dose response, 1 h per day) and body mass: [0.05 kg (95%CI, 0.00 to 0.10; P = 0.066)], change in sedentary behaviour (dose response, 1 h per day) and body mass: [0.38 kg (95%CI, -0.09 to 0.86; P = 0.111)], sedentary behaviour (dose response, 1 h per day) and waist circumference: [-0.04 cm (95%CI, -0.26 to 0.18; P = 0.715)] and sedentary behaviour (higher versus lower) and obesity risk: [OR 1.17 (95%CI, 0.77 to 1.80; P = 0.459)]. There was a significant relation for change in sedentary behaviour (dose response, 1 h per day) and waist circumference [0.27 cm (95%CI, 0.04 to 0.50; P = 0.023)]. Conclusion: Our systematic review and meta-analysis suggests that sedentary behaviour has a weak relation to measures of obesity. These findings help clarify the results of previous qualitative reviews by showing that a quantitative approach to evaluating recent and previous studies has not substantially changed the observational relation between sedentary behaviour and weight gain and obesity