Carbohydrates are necessary for glycogen replenishment, but adding carbohydrates does not enhance muscle protein synthesis Faster-acting carbohydrates may acutely increase protein synthesis faster than slower carbohydrates, but studies do not show greater increases in muscle mass with faster-acting amino acids or carbohydrates. Most studies have not shown greater increases in anabolic signaling pathways with carbohydrates.
ARE FAST-ACTING CARBS AND INSULIN SPIKES AFTER WORKOUTS BETTER FOR GAINING MUSCLE SUMMARY
- · Carbohydrates are necessary for glycogen replenishment, but adding fast acting carbs does not enhance muscle protein synthesis
- · Fast acting carbs may acutely increase protein synthesis faster than slower carbohydrates, but studies do not show greater increases in muscle mass with faster-acting amino acids or carbohydrates.
- · Most studies have not shown greater increases in anabolic signaling pathways with fast acting carbs.
FAST CARBS AFTER LIFTING
Protein and carbohydrates have distinct functions in which they stimulate a greater overall net anabolic pathway than either one alone. It has been well documented that consuming carbohydrates plus protein does not lead to greater increases in protein synthesis than protein alone.(1, 2)
Carbohydrates alone have a minimal effect on protein synthesis; however, carbohydrates have a vital role in replenishing muscle glycogen stores. Greater glycogen will give you the fuel to train harder in the next session. It was once thought that the insulin response from carbohydrates was necessary to reduce muscle tissue breakdown. However, the increased insulin from protein ingestion alone is sufficient to inhibit protein breakdown after exercise.(3)
ARE FAST ACTING CARB POWDERS AFTER EXERCISE NEEDED WITH ESSENTIAL AMINO ACIDS
In a systemic review of the literature, it was found that insulin exerted no stimulatory effect on muscle protein synthesis. Insulin only increases protein synthesis in the presence of elevated amino acids.(4) Some have suggested that carbohydrates increase anabolic signaling pathways. In a study, men who consumed 2 g/kg or .9 grams of maltodextrin per pound of body weight before exercise had increased insulin but did not increase anabolic signaling pathways (i.e., mTOR) compared to water.
The authors stated, “recreationally trained men eating a normal diet do not need to supplement with excess carbohydrates after resistance exercise since it will not dramatically increase mTOR activity despite increased insulin signaling.”
ARE FAST ACTING CARBS GOING TO SUPPRESS MUSCLE TISSUE BREAKDOWN?
Adding carbohydrates to a sufficiently high dose of protein (> 20 grams) has no additive effect on reducing muscle tissue breakdown or increasing muscle protein synthesis.(5) Thus, protein ingestion with a small amount of carbohydrates post-exercise will not enhance muscle protein synthesis. Still, It has been shown that the combination of protein and carbohydrates is superior for increasing muscle glycogen than carbohydrates or protein alone.(6)
In a 2021 study that compared carbohydrates to carbohydrates plus protein, both groups had similar increases in glycogen and anabolic signaling pathways post-exercise. However, the protein and carbohydrates group recovered faster after exercise despite similar glycogen synthesis rates.
The author suggested that the enhanced nitrogen balance in the carbohydrate and protein drinks enhanced exercise recovery independent of glycogen or anabolic signaling pathways.(7) Many older studies comparing increases in lean mass comparing carbohydrates to carbohydrates plus protein are biased because the protein and carbohydrate group is getting more protein, which impacts the results.
Some have suggested that low carbohydrates can blunt anabolic signaling pathways post-exercise, leading to less favorable muscle growth responses. The research suggests that low carbohydrates have minimal effects on molecular signaling pathways (i.e., mTOR, protein synthesis, IGF-1, etc.) in muscle.(8)
EATING CARBOHYDRATES AFTER WORKOUT
One study examined the anabolic actions of a carbohydrate drink after eccentric exercise. The authors hypothesized that the anabolic actions of insulin combined with high muscular tension would produce a synergistic effect on anabolic signaling pathways in muscle.
Subjects performed five sets of maximal eccentric contractions (~120 % of a 1-RM) and consumed either a high carbohydrate drink or water post-exercise. The carbohydrate group had greater increases in insulin and glucose post-exercise, but the anabolic signaling pathways (i.e., mTOR) were not different between the water and carbohydrate groups. The authors concluded that anabolic signaling pathways are independent of glucose/insulin levels and influenced by high muscle tension.(9)
Since resistance exercise is a potent stimulator of mTOR and protein synthesis, the combination of adequate protein and calories seems sufficient to elicit muscle hypertrophy responses irrespective of carbohydrate intake or glycogen status.(10, 11)
Figueiredo and Cameron-Smith have stated, “While it cannot be excluded that carbohydrate addition may provide benefits for recovering athletes, based on data, no further beneficial actions of carbohydrates, irrespective of glycemic index, is evident concerning muscle hypertrophy when a protein supplement that maximally stimulates muscle protein synthesis is ingested.”(12)
DO FAST ACTING CARBS INCREASE PROTEIN SYNTHESIS POST-EXERCISE?
Many have emphasized that adding fast-acting carbohydrates, such as cluster dextrin or Vitargo, spikes insulin post-exercise and enhances muscle protein synthesis rates. Some suggest that cluster dextrin and Vitargo can enhance amino acid absorption, nutrient delivery and optimize glycogen replenishment.(13, 14)
Both have low osmolality and result in a faster absorption rate than traditional glucose or maltodextrins. Researchers had subjects perform resistance exercise and immediately after exercise, received either meat protein hydrolysate with either 75 grams of cluster dextrin or glucose. At the end of the study, there was no difference in protein synthesis rates between the glucose or the cluster dextrin group.(15) These studies are similar to the different increases in amino acids with various proteins.
FAST ACTING CARBS AFTER WORKOUT TO BUILD MUSCLE
Whey protein has long been considered a fast protein with rapid increases in leucine and essential amino acids. Casein is considered a slow protein with a more moderate and longer-acting rise in amino acids. Despite the differences in rates of increase in amino acids, most studies have shown similar increases in lean muscle mass, despite the greater increases in insulin with whey protein post-exercise.(16, 17)
Two studies have compared milk protein, which contains a lower glycemic index because of lactose. However, milk still has a superior increase in protein synthesis and lean mass to soy protein.(18, 19)
The research suggests that high-molecular-weight carbohydrate powders such as Vitargo may enhance faster glycogen replace after endurance exercise; however, sprint capacity was not different between Vitargo and a traditional carbohydrate drinks.(20) Most studies have failed to show any performance benefits between high molecular weight (i.e., Vitargo, Cyclodextrin) and traditional sports drinks .(21, 22)
1. Koopman R, Beelen M, Stellingwerff T, Pennings B, Saris WH, Kies AK, et al. Coingestion of carbohydrate with protein does not further augment postexercise muscle protein synthesis. Am J Physiol Endocrinol Metab. 2007;293(3):E833-42.
2. Borsheim E, Aarsland A, Wolfe RR. Effect of an amino acid, protein, and carbohydrate mixture on net muscle protein balance after resistance exercise. Int J Sport Nutr Exerc Metab. 2004;14(3):255-71.
3. Staples AW, Burd NA, West DW, Currie KD, Atherton PJ, Moore DR, et al. Carbohydrate does not augment exercise-induced protein accretion versus protein alone. Med Sci Sports Exerc. 2011;43(7):1154-61.
4. Abdulla H, Smith K, Atherton PJ, Idris I. Role of insulin in the regulation of human skeletal muscle protein synthesis and breakdown: a systematic review and meta-analysis. Diabetologia. 2016;59(1):44-55.
5. Glynn EL, Fry CS, Timmerman KL, Drummond MJ, Volpi E, Rasmussen BB. Addition of carbohydrate or alanine to an essential amino acid mixture does not enhance human skeletal muscle protein anabolism. J Nutr. 2013;143(3):307-14.
6. Ivy JL, Goforth HW, Jr., Damon BM, McCauley TR, Parsons EC, Price TB. Early postexercise muscle glycogen recovery is enhanced with a carbohydrate-protein supplement. J Appl Physiol (1985). 2002;93(4):1337-44.
7. Dahl MA, Areta JL, Jeppesen PB, Birk JB, Johansen EI, Ingemann-Hansen T, et al. Coingestion of protein and carbohydrate in the early recovery phase, compared with carbohydrate only, improves endurance performance despite similar glycogen degradation and AMPK phosphorylation. Journal of Applied Physiology. 2020;129(2):297-310.
8. Escobar KA, VanDusseldorp TA, Kerksick CM. Carbohydrate intake and resistance-based exercise: are current recommendations reflective of actual need? British Journal of Nutrition. 2016;116(12):2053-65.
9. Figueiredo VC, Farnfield MM, Ross MLR, Gran P, Halson SL, Peake JM, et al. The Effect of Carbohydrate Ingestion Following Eccentric Resistance Exercise on AKT/mTOR and ERK Pathways: A Randomized, Double-Blinded, Crossover Study. Int J Sport Nutr Exerc Metab. 2019;29(6):664-70.
10. Camera DM, West DW, Burd NA, Phillips SM, Garnham AP, Hawley JA, et al. Low muscle glycogen concentration does not suppress the anabolic response to resistance exercise. J Appl Physiol (1985). 2012;113(2):206-14.
11. Churchley EG, Coffey VG, Pedersen DJ, Shield A, Carey KA, Cameron-Smith D, et al. Influence of preexercise muscle glycogen content on transcriptional activity of metabolic and myogenic genes in well-trained humans. J Appl Physiol (1985). 2007;102(4):1604-11.
14. Almada A, VanEck LE, Shah M, Jones M, Jagim A, Dalton R, et al. Effect of post-exercise ingestion of different molecular weight carbohydrate solutions. Part 1: The glucose and insulin response2015.
15. Nishimura Y, Jensen M, Bülow J, Thomsen TT, Arimitsu T, Van Hall G, et al. Co-ingestion of cluster dextrin carbohydrate does not increase exogenous protein-derived amino acid release or myofibrillar protein synthesis following a whole-body resistance exercise in moderately trained younger males: a double-blinded randomized contr. European Journal of Nutrition. 2022.
16. Wilborn CD, Taylor LW, Outlaw J, Williams L, Campbell B, Foster CA, et al. The Effects of Pre- and Post-Exercise Whey vs. Casein Protein Consumption on Body Composition and Performance Measures in Collegiate Female Athletes. Journal of sports science & medicine. 2013;12(1):74-9.
17. Babault N, Deley G, Le Ruyet P, Morgan F, Allaert FA. Effects of soluble milk protein or casein supplementation on muscle fatigue following resistance training program: a randomized, double-blind, and placebo-controlled study. Journal of the International Society of Sports Nutrition. 2014;11(1):36.
18. Hartman JW, Tang JE, Wilkinson SB, Tarnopolsky MA, Lawrence RL, Fullerton AV, et al. Consumption of fat-free fluid milk after resistance exercise promotes greater lean mass accretion than does consumption of soy or carbohydrate in young, novice, male weightlifters. Am J Clin Nutr. 2007;86(2):373-81.
19. Wilkinson SB, Tarnopolsky MA, Macdonald MJ, Macdonald JR, Armstrong D, Phillips SM. Consumption of fluid skim milk promotes greater muscle protein accretion after resistance exercise than does consumption of an isonitrogenous and isoenergetic soy-protein beverage. The American Journal of Clinical Nutrition. 2007;85(4):1031-40.
20. McGlory C, Morton JP. The effects of postexercise consumption of high-molecular-weight versus low-molecular-weight carbohydrate solutions on subsequent high-intensity interval-running capacity. Int J Sport Nutr Exerc Metab. 2010;20(5):361-9.
22. Mock MG, Hirsch KR, Blue MNM, Trexler ET, Roelofs EJ, Smith-Ryan AE. Post-Exercise Ingestion of Low or High Molecular Weight Glucose Polymer Solution Does Not Improve Cycle Performance in Female Athletes. J Strength Cond Res. 2021;35(1):124-31.