The purpose of the trial is to assess the effects of weight loss on functional status and lean muscle mass in frail, obese older adults (>/= 60) who participate in a 6 month weight reduction intervention. Participants will be randomized into one of two study arms: Weight Loss Control: (n = 25) subjects follow a calorie-reduction diet for a weight loss of ≥10%; or Weight Loss-High Protein: (n = 50) subjects follow a calorie-reduction diet for a weight loss of ≥10%, with a high proportion of high quality protein at each meal. Intakes of > 30g of high quality protein will be achieved three times a day by subjects in this group, predominantly all from animal sources and 60-70% of animal protein from beef. Subject criteria will include obese (>30 kg/m2) older adults (>60 yrs.) with mild to moderate functional impairment (by Short Physical Performance Battery; SPPB score >/= 4)