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If you have been lifting weights for a while, you have probably heard about the importance of ingesting simple carbohydrates during the critical post-workout window. The idea is that the insulin spike which occurs with carb consumption augments protein uptake and thus optimizes muscle building and repair.
However, there is a growing body of evidence which argues against this theory. One study which was published in Nutrition and Metabolism split older male subjects into two groups, one of which consumed only protein post-workout, while the other group consumed the identical amount of protein, with an added carbohydrate source in a 1 to 2 ratio. The subjects in the second group initially had an insulin spike and a greater uptake of protein into muscle tissue, but after several hours, both groups had the same uptake of protein.
Athletes who train several times a day may benefit from the faster rate of protein absorption which accompanies carbohydrate consumption during the post-workout window since they need to keep glycogen stores full for the next workout. However, the average person or athlete who only trains once per day will be able to replenish glycogen levels within a day or two, without any negative effects, as long as enough carbohydrates are consumed in the diet throughout each day. This is great news for individuals who cannot consume large amounts of simple carbohydrates, either due to diabetes or excess weight, because the overall absorption and uptake of protein is unaffected by carbohydrate intake.
Substances like whey protein induce an even bigger spike in insulin than carbs do, and the increase insulin levels from protein alone is adequate to inhibit the muscle breakdown which occurs post-lift. You might also consider employing a carb-cycle diet which consists of a low carb plan intermixed with one or two high carb days per week. The carb spike days will effectively replenish glycogen stores and keep your energy high for those intense lifting days, while the remaining lower carbohydrate days will boost growth hormone production.
REFERENCES: Hamer H, Wall B, Kiskini A, de Lange A, et al (2013) Carbohydrate co-ingestion with protein does not further augment post-prandial muscle protein accretion in older men. Nutrition & Metabolism 10:15.