Seventy patients with breast, colorectal or endometrial cancer will be recruited within a time period of 12 months. Patients will be randomly assigned to an intervention or a control group. The intervention group will receive standard care alongside 12 motivational interviewing sessions within 12 weeks. The control group will receive standard care only. Physical activity behaviour (3D-accelerometer) and physical fitness (cardiovascular and strength fitness) will be measured in the week preceding and following the intervention. Additionally, a subgroup from both study arms will be assessed 12 weeks after the completion of the intervention. The investigators hypothesize that sedentary time will decrease and time spent in moderate and vigorous physical activity, physical fitness and quality of life of cancer survivors will increase to a greater extent in the intervention group than in the control group. Furthermore, health-related quality of life and resource use (intervention and healthcare costs, out of pocket costs) will be measured to evaluate the cost-effectiveness of the intervention.