Casein Protein Supplementation in Trained Men and Women: Morning versus Evening

The purpose of this investigation was to determine the effects of casein supplementation (54 grams) in the morning (Casein-MOR) or evening (Casein-EVE) (90 minutes or less prior to sleep) on measures of body composition and exercise performance in trained men and women. Twenty-six healthy men and women who had been training regularly for greater than 12 months completed this 8-week study (mean±SD; Casein-MOR group [n=14, seven male, seven female]: 30.0±8.2 yr; 170.7±9.5 cm; 70.9±13.9 kg. Casein-EVE group [n=12, nine male, three female]: 28.9±9.5 yr; 172.9±7.3 cm; 72.6±10.9 kg). Subjects in each group supplemented with casein protein (54 grams) either in the morning (prior to 12:00pm) or evening (~90 minutes or less prior to sleep). Subjects were advised to not significantly alter their training program as well as to keep a diary of their workouts. Body composition was assessed via the Bod Pod®. In addition, subjects provided dietary self-reports via MyFitnessPal®. Approximately 24 daily dietary self-reports were provided from each subject that self-monitored their diet. The investigators monitored their diet throughout the study. Both the Casein-MOR and Casein-EVE groups consumed significantly more protein (post versus pre; p<0.05); however, there were no between-group differences regarding protein intake. Furthermore, there were no within- or between-group differences for any other measure. In trained subjects who did not significantly alter their training program, the addition of 54 grams of casein protein in the morning or evening had no significant effects on body composition. Furthermore, the additional consumption of protein calories did not result in an increase in fat mass despite the fact that exercise volume did not change.