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.

Inclusion Criteria:Male or female.Age above or equal to 18 years at the time of signing informed consent.Body mass index (BMI) greater than or equal to 30.0 kilogram per square meter (kg/m^2).History of at least one self-reported unsuccessful dietary effort to lose body weight.Exclusion Criteria:HbA1c greater than or equal to 48 millimoles per mole (mmol/mol) (6.5 percent) as measured by the central laboratory at screening.History of type 1 or type 2 diabetes.Treatment with glucose-lowering agent(s) within 90 days before screening.A self-reported change in body weight greater than 5 kilograms (kg) (11 pounds) within 90 days before screening irrespective of medical records.Personal or first-degree relative(s) history of multiple endocrine neoplasia type 2 or medullary thyroid carcinoma.