A Study of LY4329090 in Participants With Obesity or Overweight Who Are Otherwise Healthy

Inclusion Criteria: * Participant must be 18 (21 for Singapore site) to 65 years of age, inclusive, at the time of signing the informed consent. * Are overtly healthy with no comorbidities related to body mass index (BMI). * Have a BMI between 27.0 kilograms per square meter (kg/m²) and 40.0 kg/m², inclusive. * Have had a self-reported stable weight for 3 months prior to screening. Exclusion Criteria: * Have a history or presence of cardiovascular, respiratory, hepatic, renal, gastrointestinal (GI), endocrine, hematological, or neurological disorders. * Have a history of chronic medical conditions involving the heart, liver, or kidneys. * Have either * ongoing asymptomatic bradycardia defined as less than 50 beats per minute at screening visit * electrocardiogram (ECG) findings at screening visit of second-degree atrioventricular block or higher, or * history of symptomatic bradycardia with uncorrected etiology, including diagnosis of sick sinus syndrome. * Have an abnormal blood pressure and/or pulse rate at screening. * Have an obesity induced by other endocrinologic disorders or diagnosed monogenetic or syndromic forms of obesity. * Have any of the following: * a diagnosis of hypocalcemia or hypercalcemia, or * confirmed abnormal laboratory values for calcium and serum phosphorus. * Have a known, clinically significant gastric emptying abnormality, have undergone weight loss surgery, or have had endoscopic and/or device-based therapy for obesity or have had device removal within the last 6 months. * Have been diagnosed with type 1 or type 2 diabetes mellitus or have glycated hemoglobin A1c (HbA1c) greater than or equal to (≥) 6.5 percent (%) or 48 millimoles per mole (mmol/mol) at screening. * Have a history or presence of psychiatric disorders, within the last 2 years, that would present a safety risk or may significantly impair the participant's ability to comply with study procedures. * Have taken any glucose-lowering medications, including insulin, in the past 3 months before screening. * Have received any drugs from the incretins class within 90 days prior to screening. * Have been treated within 3 months prior to screening or plan to be treated with prescription medications that promote weight loss. * Intend to use any weight loss medications during study participation. * Prior (within 6 months) or planned (during the study) device-based treatment use for obesity.