Effectiveness of a dietary intervention on macronutrient intake, lean mass and strength gains in males participating in a supervised resistance training program

Background

ISSN recommendations for individuals involved in a general fitness program are to ingest 25-35 kcal/kg/day consisting of 3-5 g/kg of carbohydrate and ≤30% of total calories from fat. Additionally, the ISSN recommends that individuals engaged in resistance-training should ingest 1.4-2.0 g/kg/d of protein and to ingest some protein after exercise. This study examined whether nutritional counseling and post-workout supplementation affects dietary intake during training.

Methods

Eleven trained men (25±5 yrs, 180±6 cm, 82±12 kg, 14±3 %fat, training 7±4 years, 3±2 days/wk) were provided nutritional counseling by a dietitian prior to participating in a supervised resistance-training program (4 days/wk). A supplement containing 40g carbohydrate, 20g protein, and 3.5g fat was provided post-exercise. Diet records were obtained at 0, 3, 7, & 11 weeks while DEXA determined body composition, 1RM bench press, and 1RM squat measurements were obtained at 0, 4, 8, & 12 wks. Data were analyzed by ANOVA with repeated measures and are presented as means ± standard deviations.

Results

Nutritional counseling did not change energy intake (30.9±5.5, 36.4±9.6, 35.0±10.2, 33.1±6.1 kcal/kg/day; p=0.20) or fat intake (34±10, 34±6, 34±6, 34±7 %; p=0.97). Protein intake significantly increased from baseline (1.7±0.4, 2.4±0.8, 2.3±0.6, 2.4±0.5 g/kg; p=0.002) while carbohydrate intake significantly decreased (3.5±1.2, 3.3±0.6, 2.8±1.2, 2.3±0.9 g/kg; p=0.02); corresponding to an increase in percentage of protein (22±6, 26±3, 28±10, 29±6 %; p=0.03) and a decrease in percentage of carbohydrates (45±15, 38±8, 31±10, 28±9 %; p=0.003). After 4, 8 and 12 weeks, respectively, a significant increase in lean mass was observed (1.3±1.7, 2.1±1.8, 2.2±2.1 kg; p=0.001) with no significant effect on body fat percentage (14.3±2.7, 15.0±3.3, 14.7±3.5, 15.1±3.5 %; p=0.34). Bench press 1RM (-2±6, 3±6, 9±5 %; p=0.001) and squat 1RM (14±10, 33±14, 43±18 %; p=0.001) increased from baseline.

Conclusion

Nutritional counseling prior to engaging in a resistance-training program that included post exercise supplementation increased dietary protein intake and resulted in positive training adaptations despite a reduction in carbohydrate intake. Additional nutritional guidance may be necessary to ensure adequate carbohydrate intake particularly in athletes engaged in heavy training.

Funding

Supported by National Strength and Conditioning Association. Supplements provided by Cytosport^TM, Inc.