Physical activity and obesity: what we know and what we need to know

Creating a negative energy balance by decreasing caloric consumption and increasing physical activity is a common strategy used to treat obesity. A large number of review and original research papers have considered the role of physical activity in weight loss and maintenance. However, their conclusions are at times conflicting. In this review, we have critically evaluated the findings of systematic reviews and meta-analyses and supplemented their conclusions with recently published, high-quality clinical trials. We have eliminated studies that were methodologically flawed in an attempt to reduce the ambiguity in the literature. We further sought, through selective review of these publications, to isolate the effects of various types of exercise, independent of dietary interventions, to further clarify their independent contributions. Thus, our review describes (i) combined calorie restriction with physical activity interventions, (ii) physical activity interventions without calorie restriction and (iii) the role of physical activity on maintenance of weight loss. Through this critical examination of the literature, we have provided conclusions to address certain ambiguities regarding the role of physical activity in obesity treatment that will inform clinical practice. We have also identified several long-standing gaps in knowledge that will inform future research.