A Study of Retatrutide (LY3437943) Compared to Tirzepatide (LY3298176) in Adults Who Have Obesity

Inclusion Criteria: * Have obesity and a history of at least one self-reported unsuccessful dietary effort to reduce body weight. Exclusion Criteria: * Have a self-reported change in body weight \>5 kilograms (kg) (11 pounds) within 90 days before screening. * Have a prior or planned surgical treatment for obesity. * Have a prior or planned endoscopic procedure and/or device-based therapy for obesity. * Have taken weight loss drugs, including over-the-counter medications, within 90 days prior to screening. * Have a family or personal history of medullary thyroid carcinoma (MTC) or multiple endocrine neoplasia syndrome type 2 (MEN-2). * Have had within the past 90 days before screening: * acute myocardial infarction * cerebrovascular accident (stroke) * coronary revascularization * hospitalization for unstable angina, or * hospitalization due to congestive heart failure. * Have New York Heart Association Functional Classification Class IV congestive heart failure. * Have a history of chronic or acute pancreatitis.