Higher energy and carbohydrate intakes have been hypothesized to enhance resistance training adaptations, yet empirical evidence remains mixed. This study investigated whether supplemental carbohydrate-energy intake improves muscle hypertrophy, strength, and fatigue resistance in resistance-trained men.

Twenty resistance-trained men completed a quasi-randomized, double-blinded, counterbalanced crossover trial. Participants consumed either a daily protein-only supplement (30 g protein, 4 g carbohydrate) or a daily protein-plus-carbohydrate supplement (30 g protein, 54 g carbohydrate) for 8 weeks each, followed by crossover, while continuing their habitual training and diet. Primary outcomes included lean mass (dual-energy x-ray absorptiometry), muscle thickness and cross-sectional area (ultrasound), back squat one-repetition maximum, knee extensor peak torque, and fatigue index.

The carbohydrate-protein supplement produced significantly higher daily energy and carbohydrate intake compared to the protein-only supplement, with no differences in protein intake, fat intake, or training volume. No significant between-condition differences were observed for any outcome. These results suggest that modest increases in carbohydrate-energy intake outside of an energy deficit are unlikely to meaningfully enhance muscle hypertrophy, strength, or fatigue resistance in trained men.

Inclusion Criteria:

• Male sex
• Aged 18-40 years
• BMI not exceeding 35 kg/m²
• Minimum of two years resistance training experience
• Resistance training frequency of at least four days per week
• No known allergy to whey protein supplements

Exclusion Criteria:

• Known cardio-metabolic disease (e.g., clinical obesity, diabetes, hypertension, heart disease)
• Any condition contraindicating participation in resistance training
• Known allergy to whey protein supplements

De-identified individual participant data are publicly available via the Open Science Framework

Data are already available

Publicly available with no access restrictions

Participants were blinded (supplements were provided in clear, unlabeled containers). Assessors/testers were blinded to group allocation. The ultrasound technician was blinded.