Physical activity is a cornerstone in the medical management of obesity and could be important for weight loss following bariatric surgery. This review aims to describe the evolution of physical activity following massive weight loss induced by bariatric surgery, and to identify the relationship between physical activity and amount of weight loss. A literature search identified 20 publications (19 studies) reporting physical activity data in relation to bariatric surgery. All studies were observational. Self-assessment of physical activity was used in all the studies. Objective measures (pedometry) were used in two studies. The time frame for physical activity assessment varied: before surgery in two publications, after surgery in nine, and longitudinal pre- to post-operative evolution in nine. The latter nine publications found an increase in physical activity after bariatric surgery. In 10/13 studies where it was described, there was a positive relationship between physical activity level and amount of weight loss. In conclusion, observational evidence of self-reported physical activity suggests that physical activity increases after bariatric surgery and that physical activity is associated with surgically induced weight loss. However, these findings warrant further evaluation using objective measures of physical activity and testing in controlled trials.