The primary goal of this study is to determine whether adherence to a high protein (≥1.0 g/kg/d) weight loss program results in improved physical function by favorably affecting body composition compared to weight stability in obese, older adults. This will be accomplished by conducting a 24-week trial in 124 obese (BMI 30-40 kg/m2), older (65-79 years) men and women, at risk for mobility disability, randomized to either: (1) high protein intake (≥1.0 g/kg/d; n=62) during weight loss, or (2) weight-stable control (n=62).