What the research says about carbohydrates and building muscle, and how to eat for it without tracking every gram.
Do you need a big pile of carbs to build muscle? Less than gym lore says, as long as your protein is covered. Here is what the evidence shows and what to do with it.
Carbs and muscle: the short version
A 2026 meta-analysis in Sports Medicine pooled 11 studies that compared higher and lower carbohydrate intakes with protein matched. It found no significant effect on muscle growth (SMD 0.15, p = 0.23). The studies were short and small, so read it as “no clear benefit found”, not “carbs never matter”.
Key things to know
- Protein is the bigger lever. A meta-analysis of 49 trials found protein supplementation stopped adding fat-free mass beyond about 1.62 g/kg a day.
- Trained lifters grew on either diet. In an 8-week trial of 29 trained men, lean mass rose in both lower and higher carb groups, with no significant difference.
- Carbs may help specific lifts. In that same trial, only the higher-carb group improved its arm curl max significantly (+6.6% vs +3.0%).
- Timing isn’t magic. A meta-analysis of 23 studies found total daily protein predicted growth better than eating right around the workout.
- Context matters. The ISSN position stand gives 8–12 g/kg a day for athletes training at moderate to high intensity for up to 12 or more hours a week, a very different situation from a few lifting sessions.
What the evidence says
Why carbs are not the main driver
When protein is matched, extra carbohydrate did not produce measurably more muscle in the pooled data above. Carbs still fuel training. The ISSN position stand notes that carbohydrate supplementation reduces muscle glycogen loss during resistance exercise. Glycogen is the carbohydrate your muscles store for fuel.
Key takeaway: Carbs support the work you do in the gym; protein and total training do more for the muscle you build.
Why a narrow post-workout window doesn’t hold up
You don’t need to sprint to a shake. The 23-study analysis found that immediate protein around workouts added nothing once total intake was accounted for. Hit your daily number first.
How to put it into practice
- Set protein first. Aim for roughly 1.6 g/kg a day, per the 49-trial analysis.
- Spread it out. The ISSN stand favors 20–40 g per dose (0.25–0.40 g/kg), evenly spaced through the day. Our guide to protein needs after 40 shows how that looks in meals.
- Fill the rest with carbs you enjoy. Rice, oats, fruit and potatoes keep sessions fueled, and heavy or long training days may call for more.
Regular eating is the hard part. Proteinly’s automatic eating timer reminds you to eat every 2 hours, which turns spreading your protein into a habit. The protein-first approach means no calorie counting.
Frequently asked questions
Do I need carbs before or after a workout?
The evidence above doesn’t show a growth advantage for carbs timed around training. A carb-containing meal you tolerate can still help you feel fueled, since carbs limit glycogen loss during lifting.
Will low carb hurt my gains?
In the pooled data, higher carbs gave no significant hypertrophy edge. Strength on some lifts may differ, as the 8-week trial hinted for arm curls. Pick the level you can stick with.
How much protein is enough?
About 1.6 g/kg a day is where gains stopped rising in the large analysis. For when to eat it, see our piece on the best time to eat protein.
Next steps
Get protein right, keep carbs at a level that fuels your training, and stay consistent. Build the habit with Proteinly at proteinly.io, learn about the protein-first approach, and follow us on YouTube, Instagram and TikTok.