There is an extensive debate in the nutrition and fitness community about whether or not high carbs or low-carb diets are superior. This conversation has digressed into an argument that lacks context and has resulted in arguments for both camps. In order to have a productive and meaningful conversation, we must align the discussion with the goals of the athlete. Power and bodybuilding athletes are in pursuit of the best nutrition and diet to improve strength and hypertrophic muscle gain. Protein absorption from food consumption during the 24-48 hours post-training, is vital to muscle hypertrophy because amino acids balance is a crucial regulator of muscle protein synthesis (Tipton KD., Wolfe RR. 2001). Traditional wisdom suggest that post-exercise carbohydrates are ideal to ingest post training due to increases in insulin sensitivity after lifting weights; which appears to maximize the anabolic environment for protein synthesis according to Tipton et al. However, nutrient timing guidelines are based on the needs of endurance athletes and not strength and physique athletes. The needs of endurance athletes are vastly different than the needs of physique and strength athletes.
We can trace the post training carbohydrate recommendation back to a study done by Ivy, Katz, Cutler, Sherman, and Coyle in 1988 where test subjects were put through glycogen-depleting protocols to test the rate of glycogen re-synthesis from a carbohydrate solution consumed either immediately after, or two hours after the bout. The results of the study showed consumption of 2 grams of carbohydrates per kilogram, resynthesized glycogen 2–3 times faster in the group who consumed carbohydrates immediately verse the group who waited 2 hours. These findings initiated the post-exercise recommendation for carbohydrate. However, there are two problems with this recommendation as it relates to strength and physique athletes. First, endurance athletes are very interested in glycogen re-synthesis because they train the same muscle groups every day, if not multiple times per day; with the goal of maximizing performance. When examining strength and bodybuilding athletes training, the need to train the same muscle group consecutive days in a row or multiple times per day is non-existent. Post training carbohydrates are targeting glycogen re-synthesis and not protein synthesis. The second problem with this recommendation is it is based on the speed of glycogen re-synthesis and fails to examine total glycogen re-synthesis. In the study done by Jentjens and Jeukendrup it was discovered that complete glycogen re-synthesis to pre-trained levels can occur well within 24 hours given sufficient total carbohydrate intake.
The body’s response to protein metabolism last approximately 24-48 hours. Therefore, protein absorption from food consumption during the 24-48 hours post-training, is ultimately more important to muscle hypertrophy and muscle retention because amino acids balance is the determining regulator of muscle protein synthesis, not carbohydrates. That being said, a study done by Wang, Ding, Solares, Choi, Wang, Yoon, Farrar, and Ivy in 2017 found that the co-ingestion of carbohydrates with whey protein immediately following resistance training resulted in greater activation of the mTOR signaling pathway. MTOR is the central regulator of cell metabolism, growth, proliferation and survival; making it a key regulator of protein synthesis. Zhou, Luo, and Huang state that in times of any stress such as weight training and/or reduced caloric or nutrient intake, such as in preparation for bodybuilding or powerlifting contest, mTOR is inhibited. Therefore the findings of Wang at el. suggest co-ingestion of carbohydrates post training is advantageous to bodybuilders and strength athletes, by stimulating MTOR and improving protein synthesis due to the stress of caloric deficit and weight training.
The combination of resistance training and protein intake leads to the growth of muscle size and strength; granted muscle protein synthesis exceeds muscle protein breakdown. There must be a positive muscle protein balance from food intake, for anabolism to occur; otherwise, the balance remains negative and catabolic. The goal of this study is to ascertain if it is important to eat carbohydrates in conjunction with protein post exercise to enhance protein synthesis in strength and bodybuilding athletes or if the total volume of protein is most important; and carbohydrate timing is insignificant.
In the context of muscle nutrition and research, finding new ways to enhance protein synthesis and maximize muscle growth is vital to creating bigger, stronger, faster and more muscular athletes. However, beyond muscle growth for athletes, clarifying the carbohydrates debate helps us in several ways: 1.) developing optimal diets for muscle 2.) Understanding the risk reward of muscle verse optimal health 3.) Gaining a clearer understanding the MTOR pathway and its role in cell proliferation and 4.) Identifying new and safe muscle-building therapies. Therefore, the question becomes, is the benefit of ingesting carbohydrates with protein post weight training significant to increasing muscle growth?
It is hypothesized that co-ingestion carbohydrates with protein post training will maximize protein absorption and increase protein synthesis desirable for hypertrophy. As shown in the Wang at el. study, Co-ingestion of carbohydrate and whey protein increases fasted rates of muscle protein synthesis immediately after resistance exercise in rats, the ingestion of carbohydrates with protein post resistance training activates the MTOR pathway. Although insulin signaling is not needed for protein synthesis; insulin does play an important role in protein synthesis by activating mTOR via PI3K/akt pathway (“PI3K/AKT/mTOR pathway” 2017). Therefore, co-ingestion of carbohydrates post resistance training is beneficial to protein synthesis, but not for the reason previously argued by the nutrition community. Stimulating insulin by ingesting carbohydrates is not directly anabolic, it is however a powerful inhibitor of muscle protein breakdown.
- L. Ivy, A. L. Katz, C. L. Cutler, W. M. Sherman, E. F. Coyle (1988) Muscle glycogen synthesis after exercise: effect of time of carbohydrate ingestion. Journal of Applied Physiology Published 1 April 1988 Vol.64 no. 4, 1480-1485 DOI. Retrieved from: http://jap.physiology.org/content/64/4/1480.long
- Jentjens R, Jeukendrup A. (2003) Determinants of post-exercise glycogen synthesis during short-term recovery. Abstract Retrieved from: https://www.ncbi.nlm.nih.gov/pubmed/12617691
- Tipton KD, Wolf RR (2001) Exercise, protein metabolism, and muscle growth. International Journal of Sports Nutrition and Exercise Metabolism, 2001, 11, 109-132. Retrieved from: http://storre.stir.ac.uk/bitstream/1893/7628/1/896.pdf
- Wanyi Wang,Zhenping Ding,Geoffrey J. Solares,Soon-Mi Choi,Bo Wang,Aram Yoon,Roger P. Farrar,John L. Ivy (2017) Co-ingestion of carbohydrate and whey protein increases fasted rates of muscle protein synthesis immediately after resistance exercise in rats. Retrieved from: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0173809
- Hongyu Zhou, Yan Luo, Shile Huang (2011) Updates of MTOR inhibitors. Anticancer Agents Med Chem. 2010 Sep 1; 10(7): 571–581. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2980558/
- Matt McMillen (2017, November 27) Low Testosterone: How Do You Know When Levels Are Too Low? Retrieved: https://www.webmd.com/men/features/low-testosterone-explained-how-do-you-know-when-levels-are-too-low