Effects of Carbohydrates Versus Carbohydrates + Protein on Resistance Training Outcomes (CHO & PRO+CHO)

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.

Study Overview

• Status: Completed
• Conditions: Muscle Hypertrophy; Strength
• Intervention / Treatment: Dietary supplement: CHO; Dietary supplement: PRO

• Study Type: Interventional
• Enrollment (Actual): 25
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Alabama
    • Auburn, Alabama, United States, 36879-5432
      • School of Kinesiology

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

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

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Non-Randomized
• Interventional Model: Crossover Assignment
• Masking: Double

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: CHO; Daily consumption of a whey protein and maltodextrin mixture providing 30 g protein, 54 g carbohydrate, and 2 g fat per 92 g serving for 8 weeks.	Dietary supplement: CHO; Daily consumption of a whey protein and maltodextrin mixture providing 30 g protein, 54 g carbohydrate, and 2 g fat per 92 g serving for 8 weeks; Other Names: Whey protein + CHO; Dietary supplement: PRO; Daily consumption of a whey protein blend providing 30 g protein, 4 g carbohydrate, and 2 g fat per 39 g serving for 8 weeks.; Other Names: Whey protein only
Active Comparator: PRO; Daily consumption of a whey protein blend providing 30 g protein, 4 g carbohydrate, and 2 g fat per 39 g serving for 8 weeks.	Dietary supplement: CHO; Daily consumption of a whey protein and maltodextrin mixture providing 30 g protein, 54 g carbohydrate, and 2 g fat per 92 g serving for 8 weeks; Other Names: Whey protein + CHO; Dietary supplement: PRO; Daily consumption of a whey protein blend providing 30 g protein, 4 g carbohydrate, and 2 g fat per 39 g serving for 8 weeks.; Other Names: Whey protein only

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Lean mass	Bone-free lean tissue mass according to Dual-energy X-ray absorptiometry (DXA)	Baseline, 8 weeks (mid-point), 16 weeks (post)
Mid-thigh muscle thickness	Change in lateral thigh muscle thickness (vastus lateralis and vastus intermedius)	Baseline, 8 weeks (mid-point), 16 weeks (post)
Back Squat One-Repetition Maximum	Change in back squat 1RM	Baseline, 8 weeks (mid-point), 16 weeks (post)
Knee Extensor Peak Torque	Change in knee extensor peak torque using isokinetic dynamometry	Baseline, 8 weeks (mid-point), 16 weeks (post)

Collaborators and Investigators

• Sponsor: Auburn University

Study record dates

Study Major Dates

• Study Start (Actual): May 12, 2025
• Primary Completion (Actual): September 15, 2025
• Study Completion (Actual): September 16, 2025

Study Registration Dates

• First Submitted: May 15, 2026
• First Submitted That Met QC Criteria: May 15, 2026
• First Posted (Actual): May 20, 2026

Study Record Updates

• Last Update Posted (Actual): May 20, 2026
• Last Update Submitted That Met QC Criteria: May 15, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: Muscle strength; Resistance training; Energy intake; Muscle hypertrophy; Crossover trial; Carbohydrate supplementation
• Additional Relevant MeSH Terms: Amino Acids, Peptides, and Proteins; Proteins; Food; Diet, Food, and Nutrition; Physiological Phenomena; Food and Beverages; Dairy Products; Milk; Dietary Proteins; Milk Proteins; Animal Proteins, Dietary; Whey; Whey Proteins
• Other Study ID Numbers: STUDY00000295

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: De-identified individual participant data are publicly available via the Open Science Framework
• IPD Sharing Time Frame: Data are already available
• IPD Sharing Access Criteria: Publicly available with no access restrictions
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No