Effects of Casein Timing on Body Composition and Performance

In a randomized, double-blind, placebo-, exercise- and diet-controlled design, 60 subjects will participate in a 10-week study to determine the influence of selective protein timing on body composition, metabolic, and performance adaptations to resistance training. Diets will be individually standardized using the Cunningham equation adjusted for activity level to determine total maintenance calories. Carbohydrates, fats, and proteins will represent 50, 25, and 25 percent of the determined total calories. Diet counseling will occur weekly until stabilized and biweekly thereafter to ensure compliance with food and fluid intake. Protein will be distributed throughout the day as >0.30g/kg bw/meal for breakfast, lunch, and dinner. Resistance training sessions will be supervised by research staff and occur 4 times per week and begin between 7 am and 5pm. Exercises will consist of single- and multi-joint exercises for all major muscle groups (legs, chest, back, shoulders, core, and arms), be performed for 3-5 sets of 1-20 repetitions with 1-5 minutes rest between sets, and each muscle group will undergo 72-96 hours rest between training sessions within the periodized program. Protein supplements. In the treatment group, the casein supplement (40g calcium caseinate dissolved in water) will be consumed as the last meal (>2h following previous meal) before bed and the placebo (40g maltodextrin dissolved in water) either before resistance training, if training after 10am, or after resistance training, if before 10am. The control group will alternate consumption times of the casein supplement and placebo. The supplement (treatment group) or placebo (control group) will not be consumed within 3 hours of beginning or ending resistance training, nor will it be consumed within 3 hours of the first meal following waking. All groups will be provided with 0.30g/kg bw whey protein isolate immediately following training to facilitate recovery. Supplements will be consumed at a similar time of day on non-training days.

Inclusion criteria

• healthy
• trained (exercises 2-5 days per week for previous 1-3 years)
• maintains regular sleep patterns (7-9 hours per night weekly average)

Exclusion criteria

• use of ergogenic aids or medicines known to influence outcomes
• data will be excluded if a participant is <80% compliant with diet and training interventions
• consumes greater than or equal to 12 alcoholic beverages per week
• tobacco use
• dairy allergy