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.

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