Diet and Exercise Plus Metformin to Treat Frailty in Obese Seniors

Inclusion Criteria: * Age 65 - 85 years * BMI = or \> 30 kg/m2 * Mild to moderate frailty (score of 18 to 31 in the modified Physical Performance Test) * Stable body weight (plus/minus 2 kg) during the past 6 months * Sedentary (regular exercise \<1 h/wk or \<2 x/wk for the last 6 months) * Willing to provide informed consent Exclusion Criteria: * Any major chronic diseases, or any condition that would interfere with exercise or dietary restriction, or use of metformin, in which exercise, dietary restrictions, or metformin are contraindicated, or that would interfere with interpretation of results * Cardiopulmonary disease (e.g. recent MI, unstable angina, stroke) or unstable disease (e.g., NYHA Class III or IV congestive heart failure, severe pulmonary disease requiring steroid pills or the use of supplemental oxygen) that would contraindicate exercise or dietary restriction * Severe orthopedic (e.g. awaiting joint replacement) and/or neuromuscular (e.g. multiple sclerosis, active rheumatoid arthritis) disease or impairments that would contraindicate participation in exercise * Renal impairment as defined by an estimated glomerular filtration rate (eGFR of less than 30 mL/min/1.73 m2) in which metformin is contraindicated * Other significant co-morbid disease that would impair ability to participate in the exercise intervention (e.g. severe psychiatric disorder \[e.g. bipolar, schizophrenia\], excess alcohol use \[\>14 drinks per week\]) * Severe visual or hearing impairm…