A Study of Retatrutide (LY3437943) in Participants Who Have Obesity or Overweight

Inclusion Criteria: * Have body mass index (BMI) ≥30.0 kilograms per square meter (kg/m²), or ≥27.0 kg/m² with at least one of the following: * hypertension * dyslipidemia * obstructive sleep apnea, or * cardiovascular disease * History of of at least one unsuccessful dietary effort to reduce body weight GOA1 Inclusion Criteria: * Have index knee pain for \>12 weeks prior to screening, and presence of index knee pain for \>15 days over the previous month * Have knee X-ray with moderate radiographic changes (Kellgren-Lawrence Grade 2 or 3) per central reading at screening * Currently meets American College of Rheumatology (ACR) Criteria (clinical and radiological) for OA. GSA1 Inclusion Criteria: * Previously diagnosed with OSA * Have AHI ≥15 on polysomnography at screening (definition of moderate-to-severe OSA) * For participants not on positive airway pressure (PAP) therapy: unable or unwilling to use PAP therapy and have not used PAP for at least 4 weeks prior to screening. * If on PAP therapy, have been on PAP therapy for at least 3 consecutive months prior to screening, and willing to temporarily stop using PAP therapy for approximately 7 days prior to each of the sleep study (PSG) visits. GZBJ Addenda (2) inclusion criteria: * Have completed the final treatment visit of GZBJ Week 80. Exclusion Criteria: * Have a self-reported or documented change in body weight \>5 kg (11 pounds) within 90 days. * Have taken weight loss drugs, including over-the-counter medications, within 90 days prior to screening. * Have a prior or planned surgical treatment for obesity. * Have diabetes mellitus. * Have family or personal history of medullary thyroid carcinoma (MTC) or multiple endocrine neoplasia syndrome type 2 (MEN-2) * Have had pancreatitis. GOA1 exclusion criteria * Have had steroid joint injections within 90 days of screening. * Have had other joint injections and procedures within 6 months of screening. * Have joint disease other than osteoarthritis. GSA1 exclusion criteria * Use stimulants (for example, modafinil, armodafinil, solriamfetol, pitolisant, amphetamine) less than 3 months prior to screening. * Use hypnotics, mirtazapine, opioids, trazodone, and zonisamide less than 3 months prior to screening. * Use a dental appliance or other device to treat OSA other than PAP therapy. GZBJ Addenda (2) exclusion criteria * Have had study intervention discontinuation. * Have had permanent dose reduction.