Physical activity is a key to health and plays an important role in achieving weight maintenance. The purpose of this literature review was to establish how much physical activity is needed for weight stability, to prevent weight regain in previously overweight individuals and for weight loss. The PubMed database was searched for studies of physical activity and overweight or obesity up to June 2015.To be weight stable, the scientific evidence indicates that walking at least 150 minutes/week or jogging 75 minutes/week is needed. To be weight stable after major weight loss the recommendation is at least 300 minutes/week, with the possibility to decrease the time with higher intensity. To lose weight, at least 300 minutes/week complemented with a change in diet is needed. Aerobic activity is recommended; many studies indicate that »more is better«, while the magnitude of alteration in body fat by resistance training is less clear.