Participation is this study will last 1 year from screening and will include 9 study visits. During Visit 1, participants will undergo screening tests that will include a medical history, a physical exam, body measurements, a blood draw, a urine test, a GHRH+Arginine stimulation test, an electrocardiogram (ECG), and a test for the presence of blood in stool. Eligible participants will return within the next 3 weeks for an inpatient clinic stay for Visit 2. Participants will be asked to keep a food record of all food consumed during the 4 days before the second visit. Visit 2 will include a physical exam, a medical and smoking history, a review of current medications, body measurements, an overnight blood draw, a body metabolism evaluation, an oral glucose tolerance test, and two questionnaires. Also during Visit 2, participants will be assigned randomly to treatment with active GHRH or placebo. Participants will then be taught how to give themselves injections of the study drug, which will be taken daily for 12 months. Participants will also receive a 1-month supply of study drug and will be supplied with refills in subsequent study visits. Upon starting treatment, participants will undergo more testing, including a whole body DEXA scan, abdominal computed tomography (CT) scan, carotid ultrasound, and ECG.