The Role of Carbs and Muscle Growth

Low-carb diets have increased in popularity over the past few years. We now know low-carb diets are similarly effective as high-carb diets for fat loss when calories and protein are matched [1]. But what about muscle growth? Multiple recent studies investigating ketogenic diets while lifting weights found that keto diets are less effective for gaining muscle than high-carb diets [2, 3]. The studies were performed on relatively lean athletes.
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These findings may have to do with the fact that high-carb diets involve greater insulin stimulation, which may play an important role in muscle growth [4]. But what also plays a role is that it’s just harder to consume enough calories for optimal muscle growth on a keto diet. The participants in the mentioned studies (references 2 & 3) ended up consuming fewer calories when they followed a keto diet, likely because keto has mild appetite-suppressing effects [5].
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Considering this and the fact that carbohydrates play an important role in resistance training performance [6], a low-carb diet is probably not optimal for maximizing muscle growth. For a general carbohydrate guideline, check the last slide of this post. Also, I’d like to emphasize that it’s worth experimenting with a low-carb diet if you haven’t yet. But I suggest you do this while trying to lose fat. If anything, the appetite-suppressing effects of a low-carb diet help with creating a calorie deficit.
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References:
1. https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/28193517/
2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969192/
3. https://www.ncbi.nlm.nih.gov/pubmed/29986720
4. https://www.sciencedirect.com/science/article/pii/S0899900718309535
5. https://www.ncbi.nlm.nih.gov/pubmed/23632752
6. https://www.ncbi.nlm.nih.gov/pubmed/21660839