<p>Sarcopenia is the age-associated loss of muscle mass and strength. Studies have shown that combining resistance training with high protein intake increases muscle mass and strength in older adults. Women are at higher risk than men of sarcopenia. Thus, it is essential to find interventions to lessen women’s risk of losing muscle mass with aging. However, limited studies combine a specific higher-protein diet and a resistance training program in older women to determine skeletal muscle responses. This study aimed to assess the impact of a 12-week resistance training program with a high protein lean beef diet on skeletal muscle mass, strength, and quality in older women compared to a normal protein diet or a high protein diet composed of a lesser amount of beef. </p> <p>The study included three diets; a USDA recommended protein diet (0.8 g/kg/day), a high protein lean beef diet (1.4 g/kg/day), and a high protein diet composed of lesser beef (1.4 g/kg/day). Sixteen subjects were included in the study. The resistance training program consisted of leg extension, leg press, leg curl, chest press, and seated row. Muscle strength was determined by one-repetition maximum assessment at weeks one, six, and twelve. In addition, subjects underwent an MRI pre- and post-intervention to assess quadriceps volume and intermuscular adipose tissue (IMAT). Muscle quality was defined as the leg extension one-repetition maximum over the quadriceps volume. </p> <p>Muscle strength, muscle quality, and quadriceps volume increased with training in all three diet groups (P<0.05, main effect of time). No difference in muscle strength, quality, or quadriceps volume was found between the diet groups. IMAT decreased in all diet groups (P<0.05, main effect of time), but no differences were seen between the diet groups. These findings suggest that the 12-weeks of resistance training increased skeletal muscle strength, quality, and mass, independent of the normal protein or high protein diet and the source of protein in the diet.</p>