A Research Study to See How Semaglutide Helps People With Excess Weight, Lose Weight (STEP UP)

This study will look at how much weight participants will lose from the start to the end of the study. The weight loss in participants taking the investigational high dose of semaglutide will be compared to the weight loss in people taking "dummy" medicine and a lower dose of semaglutide. In addition to taking the medicine, participants will have talks with study staff about healthy food choices and how to be more physically active. Participants will either get semaglutide or "dummy" medicine. Which treatment participants get is decided by chance. Participants are more likely (4 out of 5) to get semaglutide than the "dummy" medicine. The study medicine will be injected briefly, under skin, with a thin needle, typically in the stomach, thighs, or upper arms. In the first part of the study, participants will get one injection once a week until they reach the planned dose. The second part of the study, which might last a couple of months, is a transition period, where participant will get three injections, taken right after each other, once a week. The duration of the study intervention (trial product and lifestyle intervention) will be 72 weeks followed by a 9-week follow-up period without study interventions.