The purpose of this clinical study is to look at how well a study medicine called cagrilintide helps people living with excess body weight to lose weight. Participants will either get cagrilintide, the active study medicine being tested or placebo, a medicine that has no active medicine in it. Which treatment participants get is decided by chance. Cagrilintide is a new medicine under development that doctors cannot prescribe yet, but it has been tested in humans before. Participants will be in this clinical study for about 9 months.