Gamification is commonly implemented with the goal of transforming activities, systems and services to afford similar experiences and motivational support as games do. In health and exercise contexts, the motivational support drawn from games is considered to encourage performing these activities that commonly lack motivation. However, an empirically rigorous body of literature examining the effects of gamification has been lacking. This is especially problematic in health contexts where unfounded claims can have detrimental effects. This systematic literature review of 16 comparison studies on gamification of physical activity examines what kinds of gamification have been studied in the pursuit of which outcomes, and what results the studies have attained. The results show that gamification of physical activity has provided positively oriented results; however, with more rigorous study designs the results are less optimistic. Research is focused on measuring performed physical activity, but mostly relies on self-reported data instead of objective measurement.