Post Workout Carb Intake - The Pros & Cons

Post Workout Carb Intake - The Pros & Cons




Do You Need Post-Workout Carbs to Maximize Muscle Growth?

The role of carbohydrates in sports training, health and longevity is a hot topic of debate in gyms and laboratories. Many bodybuilders utilize very low-carbohydrate diets to get ripped for shows. These diets often provoke anxiety in the athlete over the idea that this will result in loss of muscle. Let’s be clear from the start— any significant dietary energy restriction will result in the loss of hard-earned muscle. However, low-carbohydrate does not necessarily mean low energy intake. Fat and protein can make up for the lack of carbohydrate.

Multiple studies have demonstrated the benefit of very low-carbohydrate diets on markers of heart disease and metabolic syndrome. Dr. Jeff Volek and his lab at the University of Connecticut have published numerous articles on the benefits of ketogenic low-carbohydrate diets, including benefits for performance athletes.1

These diets involve consumption of carbohydrate less than 50 grams per day in most instances. Dr. Volek has demonstrated greater retention of lean body mass and improvements in fat metabolism over low-fat diets.2 He has also shown that “keto-adaptation” leads to improved handling of energy substrates during endurance exercise such that more fat is burned. When your body is “keto or fat-adapted,” meaning your brain and muscle have adapted to using ketones derived from fat for energy over carbohydrate, you are at less risk of “bonking” when your glycogen stores are depleted by intense training. This suggests that even endurance athletes could benefit from low-carbohydrate training.

However, there is always the argument that carbohydrates are needed to maintain muscle and recover after exercise. I often hear from bodybuilding gurus and trainers that, “You have to have your fast-acting carbohydrates immediately after exercise to boost insulin and muscle growth.” But does the science really support this assertion?



Glycogen Stores are Depleted After Exercise

Let’s look at the basic science first. Cell culture studies and animal research has suggested that insulin is required to get the maximal amount of muscle protein synthesis from the amino acid leucine.3 However, leucine itself has the ability to increase insulin secretion two- to three-fold over baseline.4 So if you consume whey protein, which is rich in leucine, do you even need carbs after your training?

The assertion that you need post-workout carbs likely started with literature looking into glycogen repletion after endurance exercise. After a long endurance training session, such as a long run, your glycogen stores (stored glucose) can be significantly depleted. Studies demonstrate that consumption of carbohydrate immediately after such a training session improves repletion of glycogen.5 Conversely, high-intensity resistance training bouts typically don’t cause such significant reductions in muscle glycogen— 40 percent at most. Unless you’re training again in under eight hours, that glycogen content of your muscle will be restored easily from subsequent meals before your next training bout.



Goals and Nutrition

This brings us to another question. What are your goals in training? Is your goal to be stronger and bigger (off-season)? Or is your goal to be as lean and ripped with as much muscle as possible (pre-contest diet)?

If your goal is to build as much muscle as possible, you need calories. Carbohydrates, especially fast-acting carbohydrates, cause large rises in insulin levels. When insulin levels rise, glucose and amino acids are rapidly shuttled into muscle cells and the muscle-building machines are turned on. However, the storage machinery in fat is also turned on so any excess energy intake that isn’t incorporated into muscle will be incorporated into fat. Combining protein, carbohydrate and creatine in a pre/post-workout supplement has been shown to be beneficial to building muscle over consuming it at other times in the day.6 If your goal is to just build, why wait to eat your post-workout meal? Eat and grow.

Alternatively, in order to maintain fat burning, it is best to be in a low-insulin, low-circulating carbohydrate state. If your insulin levels are significantly elevated and there’s plenty of glycogen in your muscle, a few things happen. First, the insulin shuts down the enzymes that mobilize fats. Second, the insulin turns on enzymes that store fats. Third, your muscle prefers to use glycogen (glucose) for energy when it is available. Therefore, it will burn more energy from glycogen than any other substrate. If you want to burn fat, you need to force your muscle to need fat. This requires depletion of glycogen.

Again this brings us to the question as to whether we need glucose and insulin to perform in the gym and prevent the breakdown of muscle when dieting. It is true that heavy and intense resistance training can reduce performance in a same-day second training session.7 However, studies show that when consuming a low-carbohydrate diet, your muscle can become adapted to using intramuscular triglycerides during heavy resistance exercise.8 Studies also show that performance in the gym may suffer to a small extent from glycogen depletion during energy restriction.9 If your goal is to improve the strength of your lifts AND build muscle, you are dealing with opposing forces and you’ll probably need to reassess your goals. For those who like their carbs, one study did show that if you replace dietary fat with protein and maintain carbohydrate intake during caloric restriction, resistance-trained individuals can maintain nearly all of their muscle.10 But was it really the maintenance of carbohydrate or the added protein that spared the muscle?

One might suggest that glucose and insulin prevent the breakdown of muscle during training. One study by Børsheim et al. did demonstrate that 100 grams of carbohydrate post-workout does cause increases in insulin and reductions in muscle degradation.11 However, studies also demonstrate that adequate consumption of essential amino acids after training causes an increase in insulin that can also limit protein degradation.12 Even in the highly catabolic fasted training state, with adequate post-exercise carbohydrate, protein and leucine anabolic supercompensation can occur.13 But is it the carbohydrate or the protein that is most important?



Protein or Carbs

Studies that have evaluated the post-exercise anabolic response to a combined protein and carbohydrate supplement have failed to show benefit over adequate protein alone.14 When high-quality protein like whey hydrolysate is consumed, muscle protein synthesis can be maximized without additional carbohydrate. Only small elevations in circulating insulin are required to maximize muscle anabolism and amino acids can stimulate this level of insulin release without carbohydrate present.14 It has been suggested that the leucine content of a protein can determine its ability to maximally stimulate muscle protein synthesis.15 As we have discussed in previous MD articles, the leucine breakdown product HMB can also prevent muscle catabolism in times of energy restriction.

One study on waxy maize starch and maltodextrin is worth mentioning here. Roberts and colleagues at the University of Oklahoma examined the effect of consuming a waxy maize starch versus maltodextrin prior to an intense and exhausting cycling bout.16 What they found was quite interesting. Maltodextrin caused a higher spike in blood glucose and insulin than the waxy maize. Although waxy maize might be of benefit to endurance cycling as it allows for more fat-burning efficiency over maltodextrin (less insulin response), it may not be best for getting an insulinotropic response for muscle anabolism.

Further supporting the importance of protein quality over carbohydrate is a study comparing soy and casein. When a soy supplement with rapidly absorbed maltodextrin was compared to a casein supplement containing similar amounts of slowly absorbed lactose, the casein group still demonstrated higher protein synthesis rates. Once again, the insulin response after exercise is less important than the availability of leucine.15,18 It takes pharmacological doses to see an effect from insulin beyond what occurs with consumption of protein (some bodybuilders have already figured this out).19



Factors to Consider

In summary, deciding whether to consume carbohydrates after your training session depends on a number of factors:



1. Your main objective:

If you are looking to build muscle without concerns about your fat burning, by all means, get your carbs, protein and creatine after your training. With all the added blood flow to your muscles and up-regulated glucose/amino acid transport mechanisms, why not saturate your muscle immediately after your training.

However, if your goal is to burn fat and you are utilizing a glycogen-depleted state to burn more of the fat, why spike insulin right after your training session? Let the fat-burning machinery run for a while after your training with a more moderate rise in insulin obtained from post-workout protein. If you want to build muscle without gaining much fat, get as much of your added calories from whey protein as you can tolerate.17

If your goal is to perform your best over two-per-day training sessions less than eight hours apart, utilize carbohydrate immediately after your training to restore glycogen levels before your next training session. That is, if your goal is to perform your best in the second session.

2. Your total macronutrient goals for the day:

If you are trying to maintain a low-carbohydrate diet for ketogenesis, it is likely that your carbohydrate will be evenly distributed into your veggies for the day and having a bolus of carbs after your training won’t be feasible. Data shows that you don’t need the added carbs to maximize muscle protein synthesis post-workout.

If you are consuming carbohydrates in your meals, plan to have one of your meals immediately after your training. Even though there are conflicting studies about post-workout protein and carbohydrate timing, the studies that showed no effect didn’t necessarily show a negative effect. Thus since some studies show no effect and others show a positive effect of immediate protein and carbohydrate supplementation, what do you have to lose by trying?





References:

1. Noakes T, Volek JS, Phinney SD. Low-carbohydrate diets for athletes: what evidence? Br J Sports Med. 2014 May 26.

2. Volek JS, et al. Carbohydrate restriction has a more favorable impact on the metabolic syndrome than a low fat diet. Lipids. 2009 Apr;44(4):297-309.

3. Anthony JC, et al. Contribution of insulin to the translational control of protein synthesis in skeletal muscle by leucine. Am J Physiol Endocrinol Metab. 2002 May;282(5):E1092-101.

4. Morifuji M, et al. Comparison of different sources and degrees of hydrolysis of dietary protein: effect on plasma amino acids, dipeptides, and insulin responses in human subjects. J Agric Food Chem 2010, 58(15):8788–8797.

5. Ivy JL, et al. Muscle glycogen synthesis after exercise: effect of time of carbohydrate ingestion. J Appl Physiol 1988, 64:1480–1485.

6. Cribb PJ, Hayes A. Effects of supplement timing and resistance exercise on skeletal muscle hypertrophy. Med Sci Sports Exerc 2006, 38:1918–1925.

7. Campbell BI, et al. Nutrient Timing for Resistance Exercise. Strength Cond J. August 2012, 34(4): 2–10

8. Essen-Gustavsson B, Tesch PA. Glycogen and triglyceride utilization in relation to muscle metabolic characteristics in men performing heavy-resistance exercise. Eur J Appl Physiol 1990, 61:5–10.

9. Walberg JL, et al. Macronutrient content of a hypoenergy diet affects nitrogen retention and muscle function in weight lifters. Int J Sports Med 1988, 9:261–266.

10. Mettler S, Mitchell N, Tipton KD. Increased protein intake reduces lean body mass loss during weight loss in athletes. Med Sci Sports Exerc 2010, 42:326–337.

11. Børsheim E, et al. Effect of carbohydrate intake on net muscle protein synthesis during recovery from resistance exercise. J Appl Physiol 2004, 96(2):674–678.

12. Staples AW, et al. Carbohydrate does not augment exercise-induced protein accretion versus protein alone. Med Sci Sports Exerc 2011, 43(7):1154–1161.

13. Deldicque L, et al. Increased p70s6k phosphorylation during intake of a protein-carbohydrate drink following resistance exercise in the fasted state. Eur J Appl Physiol 2010, 108:791–800.

14. Koopman R, et al. Coingestion of carbohydrate with protein does not further augment postexercise muscle protein synthesis. Am J Physiol Endocrinol Metab 2007, 293:E833–E842.

15. Norton LE, Wilson GJ: Optimal protein intake to maximize muscle protein synthesis: examinations of optimal meal protein intake. Agro Food Industry Hi-Tech 2009, 20:54–57.

16. Roberts MD, et al. Ingestion of a high-molecular-weight hydrothermally modified waxy maize starch alters metabolic responses to prolonged exercise in trained cyclists. Nutrition. 2011 Jun;27(6):659-65

17. Antonio J, et al. The effects of consuming a high protein diet (4.4 g/kg/d) on body composition in resistance-trained individuals. J Int Soc Sports Nutr. 2014 May 12;11:19

18. Hartman JW, 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):373–381.

19. Hillier TA, et al. Extreme hyperinsulinemia unmasks insulin's effect to stimulate protein synthesis in the human forearm. Am J Physiol 1998, 274(6 Pt 1):E1067–1074.