Timing of post-exercise protein does not affect gains in lean mass but may influence loss of fat mass in women

Background Women are at heightened risk for loss of strength and functional ability due to sarcopenia as they age. Resistance training (RT) is an effective intervention against muscle loss, while ingestion of a post-exercise protein supplement may have an additive effect on muscle growth. Purpose The purpose of this study was to determine if timing of protein intake following RT would influence gains in lean mass in women. Methods Fifteen women (age 38 ± 10 years, BMI 27.8 ± 5.1 kg/m2) completed 12 weeks of RT three times a week (36 sessions). Immediately (T0) or two hours (T2) after each training bout they received a high protein supplement (150 kcal, 25g protein, 5g carbohydrate, 3.5g fat). Maximal strength (1RM chest and leg press) and body composition (air displacement plethysmography) were measured at baseline and after completion of week 12. Results There were no significant differences between groups for gains in strength and lean mass. Both groups experienced similar increases in strength (P < 0.01) and gained an average of 0.43 ± 0.3 kg lean mass (P = 0.11). A significant difference between groups was observed for fat mass. Group T2 lost a significant amount of fat mass (-0.8 ± 0.6 kg) (P = 0.03) compared to Group T0 (-0.1 ± 0.7 kg). Conclusion In women engaged in a 12-week RT program, gains in lean mass are not affected by the timing of protein intake post exercise. However, a two-hour delay in intake following RT sessions results in significant decreases in fat mass.