Effect and Safety of Semaglutide 2.4 mg Once-weekly as Adjunct to Intensive Behavioural Therapy in Subjects With Overweight or Obesity

This study will look at the change in participant's body weight from the start to the end of the study. This is to compare the effect on body weight in people taking semaglutide (a new medicine) and people taking "dummy" medicine. Together with the medicine, the participant will also be part of an intensive lifestyle program where the participant will have talks with study staff about healthy food choices, what the participant can do to lose weight and be more physically active. The participant will either get semaglutide or "dummy" medicine - which treatment the participant gets is decided by chance. The participant will need to take 1 injection once a week. The study medicine is injected with a thin needle in a skin fold in the stomach, thigh or upper arm. For the first 2 months the participant will be on a low calorie diet. The diet is made up of bars, shakes and 1 low calorie pre-prepared meal for each day. The study will last for about 1.5 years. The participant will have 32 clinic visits with the study doctor.