Lots of bodybuilders, most of them I would say, emphasize the need for a substantial amount of dietary carbohydrates to build muscle. The argument takes one or both of two forms; 1) that you need carbs to perform more intense exercise in the gym; and 2) carbs are needed to raise insulin and stimulate muscle growth. I’ve never found the arguments all that compelling, but then I’m just an average gym rat, not a bodybuilder extraordinaire. So how much truth is there in these statements?
First, as for intensity of workouts. A study was recently published in the Journal of the International Society of Sports Nutrition – which I noted here – which looked at elite level gymnasts. After 30 days on a ketogenic diet, i.e one with a very low carbohydrate content, probably under 50 grams a day, the athletes’ strength and power had not diminished. However, even these elite athletes, who one would presume were already in terrific shape, lost about 2 kg of fat, with a “non-significant” increase in muscle. This shows that if anything, at least for gymnasts, who require a high level of strength, the ketogenic diet was better than their regular diets. The authors conclude:
Despite concerns of coaches and doctors about the possible detrimental effects of low carbohydrate diets on athletic performance and the well known importance of carbohydrates there are no data about VLCKD and strength performance. The undeniable and sudden effect of VLCKD on fat loss may be useful for those athletes who compete in sports based on weight class. We have demonstrated that using VLCKD for a relatively short time period (i.e. 30 days) can decrease body weight and body fat without negative effects on strength performance in high level athletes.
Assuming that the same holds for bodybuilders, let’s move on to muscle hypertrophy. Another recent study found that carbohydrate does not augment exercise-induced protein accretion versus protein alone. In this study there were two conditions: young men performed resistance training followed by ingestion of either 25 grams of whey protein, or 25 grams of whey plus 50 grams of carbohydrate (maltodextrin). Despite the fact that the extra carbohydrate raised blood glucose levels 17.5 times higher and insulin levels 5 times higher (that is, area under the curve) than protein alone, no difference was found in either muscle protein synthesis or muscle protein breakdown.
So as long as you get adequate protein, you’ve maximized the amount of hypertrophy you can get out of resistance training. Protein raises insulin, which is required for hypertrophy, but raising insulin further does nothing.
Finally there’s an interesting new study, one the co-authors of which is Jeff Volek, who’s done so much great work in this area. The effects of ketogenic dieting on skeletal muscle and fat mass. One reason why it’s interesting is that the men in the study were already resistance-trained. Normally in studies like this they like to use newbies, as you see greater results in them; if already trained subjects are used, and there’s a difference between groups, then you know it really worked well.
Twenty-six college aged resistance trained men volunteered to participate in this study and were divided into VLCKD (5 % CHO, 75 % Fat, 20 % Pro) or a traditional western diet (55 % CHO, 25 % fat, 20 % pro). All subjects participated in a periodized resistance-training program three times per week….
Results: the ketogenic diet group gained 4.3 kg lean mass (muscle) compared to only 2.2 kg for the traditional diet group; the ketogenic group lost 2.2 kg of fat, compared to 1.5 kg in the traditional group.
I’d say this last study puts to rest any argument for lots of carbohydrates in weightlifting. The very low carbohydrate ketogenic diet was superior to a diet with 55% carbohydrate. Note that protein percent was the same for both groups.
Finally, there’s a very good book I recommend by the above-mentioned Jeff Volek and co-author Stephen Phinney, The Art and Science of Low Carbohydrate Performance. I discussed it briefly here.
So, no, carbohydrates are not needed to build muscle, and in fact muscle building might be even better without them.