Carbs and Muscle Growth: More Fuel, Same Hypertrophy?

A lot of lifters assume more carbs means more muscle. This article walks through a 2025 meta-analysis asking whether higher carbohydrate intake actually improves hypertrophy when protein is kept the same.

Overview

• What did they test? The authors tested whether carbohydrate intake affects muscle hypertrophy during resistance training. 
• What did they find? Higher carbohydrate intake did not significantly increase hypertrophy (SMD = 0.15; p = 0.23), and results stayed non-significant in isocaloric comparisons and in the small subset using direct ultrasound measures.
• What does it mean for you? These data suggest no hypertrophy advantage from simply pushing carbohydrates higher when protein is matched, but the evidence is weak and heavily dependent on short, small studies and outcomes that often rely on lean mass proxies rather than direct muscle size.

What’s the Problem?

Carbohydrates, in theory, have a strong case for being beneficial for muscle hypertrophy. They are the primary substrate for high-intensity resistance training, they restore muscle glycogen, and in turn they could help sustain training quality and improve total volume over a training cycle. 

Indeed, a previous systematic review and meta-analysis in 2022 found that acute carbohydrates increase training volume, but noted that it is more likely to improve performance when sessions exceed 45 minutes and/or when you haven’t eaten in 8 hours 1. Similarly, a narrative review by the same authors of the article under review noted that carbohydrates may be beneficial during fasted training and with workouts with more than 10 sets per muscle group or with twice-a-day training 2. They also recommend consuming at least 15g of carbohydrates within three hours of training and suggest up to 1.2g/kg/hour may be needed if the workouts consist of >10 sets per muscle group or if you’re doing multiple workouts per day 2. 

The current meta-analysis expands and refines the literature, by shifting the focus from short-term performance effects toward the longer-term question lifters care about most: whether higher carbohydrate intake translates into greater hypertrophy, using training interventions lasting at least six weeks.

Purpose

This meta-analysis aimed to assess whether a higher carbohydrate intake influences muscle hypertrophy under protein-matched conditions.

Hypothesis

Carbohydrate intake would not significantly influence hypertrophy.