The evidence-led answer
NST verdict
No, you do not need carbohydrate specifically to build muscle. When protein and total calories are adequate, studies of low carb and even ketogenic diets in trained people find similar muscle and strength gains to higher carb diets. What carbs mainly do is make hard training easier: they refill muscle glycogen and support harder, repeated effort work, the training volume that drives growth. Cutting carbs very low can make demanding sessions feel harder, and because low carb diets tend to blunt appetite, it can quietly put you in a calorie deficit, and it is the deficit, not the missing carbs, that costs muscle. Eat enough total food and enough protein, include some carbs around hard training, and pick the carb level you can stick to.
Can you build muscle without carbs?
Yes. In resistance trained people, pooled analyses of ketogenic diets, the most extreme form of carb restriction, found no significant difference in fat free mass between the ketogenic diet and a higher carb control when calories were not deliberately restricted, and no significant difference between ketogenic and control diets for one rep max squat or bench press. If a diet as restrictive as keto does not clearly impair muscle or strength when protein and energy are adequate, a milder low carb approach will not either.
So why do people lose muscle on keto?
Because of the calorie deficit that usually comes with it, not the lack of carbs. A pooled analysis of 13 randomised trials in resistance trainees found ketogenic diets caused more fat loss and more fat free mass loss, around 1.3 kg, than non ketogenic diets, and adding resistance training did not rescue the fat free mass loss, but those trials were largely weight loss studies. Very low carb eating drops water weight and strongly suppresses appetite, so people often eat less without meaning to and end up in a deficit. As the body recomposition article covers, training in a calorie deficit blunts muscle gain and a large deficit costs lean mass. The carbs are not the villain; the unplanned deficit is.
What do carbs actually do for training?
Carbs are the main fuel for hard, repeated efforts. They stock muscle glycogen, and low carbohydrate availability can reduce performance in harder and repeated effort work, the kind of volume that drives muscle growth. In practice a very low carb diet can make your hard sets feel harder and your work capacity drop, especially early on before you adapt. The reassuring part: any strength or power cost from a low carb diet is small when protein intake is kept adequate. The diet does not break training. It just makes the demanding parts less comfortable.
Is there any advantage to eating low carb for muscle?
No. There is no muscle building benefit to restricting carbohydrate. Ketogenic diets in trained people also tend to have poor long term adherence, since people find the restriction hard to sustain, and over months, the diet you actually stick to matters far more than any acute metabolic difference.
How many carbs do you need?
There is no specific carb target for building muscle. The levers that matter are enough total energy and enough protein; see the protein article for the numbers. Beyond that, carbohydrate is flexible: eat the amount that lets you train hard and that you can maintain. If you train intensely, having some carbs in the meals around your session supports the work and recovery. If you prefer fewer carbs, that is fine as long as protein and calories are covered.
What this means in practice
Do not restrict carbs in the hope of building more muscle, because there is no advantage. Set your protein and total calories first. Then choose a carb level you can sustain; if you train hard, include some carbohydrate in the meals around training to fuel the sessions. If you go low carb or keto, watch that you are not slipping into an unintended calorie deficit, since it is easy to when appetite drops, because that deficit is what would cost you muscle. Expect hard sessions to feel tougher for the first few weeks of a big carb cut.
Practical meaning
There is no muscle building advantage to restricting carbohydrate. Set protein and total calories first (see the protein article). Then pick a carb level you can sustain; if you train hard, put some carbohydrate in the meals around training to fuel the sessions and recovery. On a low carb or ketogenic diet, watch for an unintended calorie deficit from reduced appetite, since that deficit, not the low carbs, is what would cost muscle. Expect hard sessions to feel harder for the first few weeks of a large carb cut.
Limitations and uncertainty
Most of this evidence is about ketogenic diets specifically, not moderate low carb eating; the ketogenic case is the hardest test. Participant numbers in the muscle and strength pooled analyses are small and the trials short. The claim that keto muscle loss runs through an unintended deficit is a reasoned synthesis, not a trial that isolated it. This is about muscle and strength, not weight loss, endurance, or health markers.
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