Amount of dietary protein consumed during caloric restriction may be a key determinant in maintaining fat-free mass during weight loss. Adequate dietary protein is essential for skeletal muscle anabolism; and, epidemiological evidence in older adults point to a salutary effect of protein intake above the current RDA (0.8 g/kg/day) on body composition. Indeed, a recent position statement by the PRO-TAGE study group advises consumption of 1.0-1.2 g/kg/d in older adults during weight-stable conditions to aid in the maintenance of lean body mass and function. Practical achievement of this level of protein intake is often difficult for obese, older adults undergoing weight loss, yet may be critical to offset weight loss-associated lean mass loss. Preliminary data from our group show a lean mass sparing effect of high protein consumption during caloric restriction. In post-menopausal women undergoing a 5-month intentional weight loss program, consumption of a high (1.2 g/kg/day) versus low (0.6 g/kg/day) protein diet was associated with 50% attenuation (17% vs. 37%) of lean mass loss. While promising, results have yet to be translated to functional changes in a tightly controlled trial of weight loss in obese, older adults.