Comparative Effects of Different Carbohydrate–Protein Formulations on Resistance Training Adaptations in Healthy Young Men

Background/Objectives: Evidence is limited on whether carbohydrate formulations enhance resistance training adaptations when protein intake is relatively adequate. This study compared two carbohydrate–protein formulations in healthy young men. Methods: In this randomized, double-blind, placebo-controlled trial, 36 untrained men aged 18–25 years were assigned to a maltodextrin-based carbohydrate control group (PLA), low-molecular-weight carbohydrate plus protein (LMW-CHO+PRO), or high-molecular-weight carbohydrate plus protein (HMW-CHO+PRO). Thirty-three participants completed 8 weeks of supervised resistance training three times weekly and daily supplementation (50 g). Body composition, muscle circumference and thickness, strength, and serum testosterone, cortisol, and testosterone-to-cortisol ratio were assessed before and after intervention. The trial was registered with the Chinese Clinical Trial Registry (ChiCTR2500110509). Results: Body mass, total muscle mass, muscle circumference and thickness, and strength improved in all groups. Both supplementation groups showed greater improvements than PLA across several muscular adaptation measures. Time × group interactions were significant for body mass and total muscle mass, but not fat mass. HMW-CHO+PRO produced greater increases in body mass and total muscle mass than LMW-CHO+PRO; however, no consistent differences between formulations were observed in regional muscle circumference, muscle thickness, strength, or blood biomarkers. Conclusions: Under conditions of relatively adequate protein intake, combined carbohydrate and protein supplementation may provide additional support for resistance training adaptations. These findings do not establish an overall advantage of either formulation, nor can the observed differences be attributed specifically to carbohydrate molecular weight.