A Study of the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of MK-5823 in Overweight or Obese Participants Who Are Healthy or Have Type 2 Diabetes Mellitus (MK-5823-002)

Inclusion Criteria: * Male or female of non-childbearing potential * A Body Mass Index between 27 and 35 kg/m\^2 and weighs at least 50 kg * Judged to be in good health and for the T2DM Panels, good health other than the diagnosis of T2DM * For T2DM Panels only: has a diagnosis of T2DM and is being treated with lifestyle management (e.g. diet and exercise) alone or in combination with a stable dose of metformin * A nonsmoker and/or has not used nicotine or nicotine-containing products for at least approximately 6 months Exclusion Criteria: * History of stroke, chronic seizures or major neurological disorder * History of clinically significant gastrointestinal, cardiovascular, hematological, hepatic, immunological, renal, respiratory, or genitourinary abnormalities or diseases. * History of clinically significant endocrine abnormalities or diseases (including type I or type II, or steroid-induced diabetes for healthy participant panel; and excluding T2DM for the T2DM Panels) * Irritable bowel syndrome, or recurrent nausea, vomiting, diarrhea, or abdominal pain. * History of neoplastic disease * History of cataracts, diabetic retinopathy, macular edema, macular degeneration, vitreous hemorrhage, glaucoma, ocular surgery, ocular trauma or blindness * Requires treatment with systemic or ocular corticosteroids * For T2DM Panels, a history of hypoglycemic unawareness * For T2DM Panels, active treatment with any anti-hyperglycemic drug other than metformin * For T2DM Panels, treatment with any peroxisome proliferator-activated receptor-gamma agonist (e.g. Avandia or Actos) within 12 weeks of study participation * Unable to refrain from using any medication beginning 2 weeks before study participation * Consumes excessive amounts of alcohol (\>3 per day) * Consumes more than 6 caffeinated beverages per day * Had major surgery or donated or lost more than 1 unit of blood * Participated in another investigational study within 4 weeks of study participation * History of significant multiple and/or severe allergies or anaphylactic reaction * Hypersensitivity to glucagon or insulin * Uses illicit drugs or has a history of drug or alcohol abuse within 3 months of study participation * Woman of child-bearing potential or is a nursing mother * For T2DM Panels, age \>50 years