This study is being conducted to see if semaglutide tablets can be used as a treatment to help people living with overweight or obesity lose weight. This study will look at the change in participants body weight. Participants will either get semaglutide tablets (new medicine) or placebo tablets ('dummy' medicine that looks like semaglutide but has no effect on the body). For a fair comparison, people are divided into two groups at random by a computer. This process is called randomisation. Semaglutide tablets are new medicine being tested to treat overweight and obesity. Doctors in many countries can already prescribe semaglutide tablets at lower doses to treat type 2 diabetes. Participants will get semaglutide or placebo tablets for 68 weeks and will need to take 1 tablet every morning In addition to taking the medicine, participants will have talks with study staff about: * healthy food choices * how to be more physically active * what participants can do to lose weight The study will last for about 1½ year.Participants will have 14 clinic visits and 7 phone calls with the study doctor. Blood samples will be taken at 10 visits. Participants will have a test to check their heart done at 3 visits. Women cannot take part if pregnant, breast-feeding or plan to get pregnant during the study period. If participant is a woman and is able to become pregnant, participant will be checked for pregnancy via urine tests.