Resistance training and maintenance of a higher protein diet have been recommended to help older individuals maintain muscle mass. This study examined whether adherence to a higher protein diet while participating in a resistance-based exercise program promoted more favorable changes in body composition, markers of health, and/or functional capacity in older females in comparison to following a traditional higher carbohydrate diet or exercise training alone with no diet intervention. In total, 54 overweight and obese females (65.9 ± 4.7 years; 78.7 ± 11 kg, 30.5 ± 4.1 kg/m², 43.5 ± 3.6% fat) were randomly assigned to an exercise-only group (E), an exercise plus hypo-energetic higher carbohydrate (HC) diet, or a higher protein diet (HP) diet. Participants followed their respective diet plans and performed a supervised 30-min circuit-style resistance exercise program 3 d/wk. Participants were tested at 0, 10, and 14 weeks. Data were analyzed using univariate, multivariate, and repeated measures general linear model (GLM) statistics as well as one-way analysis of variance (ANOVA) of changes from baseline with [95% confidence intervals]. Results revealed that after 14 weeks, participants in the HP group experienced significantly greater reductions in weight (E -1.3 ± 2.3, [-2.4, -0.2]; HC -3.0 ± 3.1 [-4.5, -1.5]; HP -4.8 ± 3.2, [-6.4, -3.1]%, = 0.003), fat mass (E -2.7 ± 3.8, [-4.6, -0.9]; HC -5.9 ± 4.2 [-8.0, -3.9]; HP -10.2 ± 5.8 [-13.2, ⁻7.2%], < 0.001), and body fat percentage (E -2.0 ± 3.5 [-3.7, -0.3]; HC -4.3 ± 3.2 [-5.9, -2.8]; HP -6.3 ± 3.5 [-8.1, -4.5] %, = 0.002) with no significant reductions in fat-free mass or resting energy expenditure over time or among groups. Significant differences were observed in leptin (E -1.8 ± 34 [-18, 14]; HC 43.8 ± 55 [CI 16, 71]; HP -26.5 ± 70 [-63, -9.6] ng/mL, = 0.001) and adiponectin (E 43.1 ± 76.2 [6.3, 79.8]; HC -27.9 ± 33.4 [-44.5, -11.3]; HP 52.3 ± 79 [11.9, 92.8] µg/mL, = 0.001). All groups experienced significant improvements in muscular strength, muscular endurance, aerobic capacity, markers of balance and functional capacity, and several markers of health. These findings indicate that a higher protein diet while participating in a resistance-based exercise program promoted more favorable changes in body composition compared to a higher carbohydrate diet in older females.