Many athletes, recreational and competitive are interested in building muscle mass. Most people have spent much time and energy focusing on dietary protein and supplements to reach this goal. However, simply ramping up protein intake will not significantly increase muscle mass. A key component to building mass is carbohydrates — a protein sparing nutrient.
The discussion on ingesting adequate carbohydrates versus more protein can be broadly viewed from two points. Muscle tissue maintenance/repair and performance, acutely and chronically.
In the literature dietary protein has been extensively studied with its relationship to building and maintaining lean body mass. Often the relationship of carbohydrates and preservation of lean mass is understated.
Too little carbs leads to muscle breakdown
In the presence of inadequate caloric or carbohydrate intake or high-intensity exercise training, energy delivery can be shifted from glycogenesis to gluconeogenesis, the process of utilizing non-carbohydrate sources to synthesize glucose. Usually, the body does not use protein as a substantial energy source. When the body has no glucose available it can take amino acids from muscle tissue for energy production. As the body starts to use muscle tissue for energy, there may be a loss of muscle mass. This most likely occurs during periods of starvation or chronic wasting illness however as stated above can occur from reduced calorie and/or carbohydrate diets. Additionally, high volume physical activity may impact this too.
Given that carbohydrate consumption is directly related to the stores of muscle glycogen it is important for individuals to maintain adequate caloric and carbohydrate intake to prevent gluconeogenesis. Even though pre-and post-exercise dietary protein is important in building and maintaining muscle mass and strength, it is not the only macronutrient of importance. In fact, too much dietary protein (amino acids) may serve no purpose in regards to building muscle mass and may harmful.
What we learned in bed
In studies on prolonged bed rest (inactivity and microgravity), Padden-Jones et al. have stated that even though dietary protein can maintain adequate nitrogen balance it may not prevent muscle loss. They further state that carbohydrate ingestion will raise insulin. If amino acid precursors are present such as with the ingestion of protein, it will stimulate amino acid uptake and protein synthesis (building lean mass). According to Padden-Jones, the combined effect of essential amino acids and carbohydrate on protein synthesis are greater than their independent effects. Both are best.
Resistance training is a carb-based activity
Due to its short duration, we associate resistance training (RT) with bioenergetic systems of ATP/CP. However, as RT volume increases the demand for energy we find an increased stimulus of glycogenolysis and glycolysis.
Carbohydrates are the body’s only macronutrient that can metabolize energy without the presence of oxygen. Given that RT is primarily an anaerobic activity its primary source of energy for performance is carbohydrates. Data has indicated that depletion of muscle glycogen takes place with higher intensity RT. A study by Robergs et al. had subjects perform 6 sets of leg extensions at 35 and 70% of 1RM. The subsequent analysis of muscle glycogen stores revealed a decrease of 38% and 39% respectively. In another study MacDougall at al. had individuals perform bicep curls at 3 sets of 10 repetitions at 80% of 1RM. The results showed glycogen concentrations reduced by 35%.
Fewer carbs lower performance – fewer gains
Given that carbohydrates are an energy source for RT one would need to consider performance when carbohydrates are restricted and replaced with more protein. If the increased consumption of dietary protein results in a lower dietary carbohydrate intake then performance could be compromised not only acutely but also chronically. A study by Haff et al. looked at carbohydrate supplements and the effects on repeated RT sessions. The study demonstrated that athletes engaging in high-intensity RT have a performance advantage with carbohydrate ingestion versus placebo due to greater glycogen resynthesis during recovery. This is important as reduced ability to perform work will reduce the capacity to make optimal gains in an RT program.
So what’s a weight lifter to-do?
McCardle and colleagues (2015) present nutrient timing for optimal muscle response for resistance training as a 3-phase process. It’s goal is to blunt the catabolic state and activate natural muscle building hormones.
Phase 1: The energy phase
This phase enhances nutrient intake to spare muscle glycogen and protein. It is also allowing for adequate muscular endurance, limiting immune system suppression, reductions in muscle damage, and improving post-training recovery.
Immediate pre- and during exercise nutrition is important. Ingesting 20-26 grams of high-glycemic carbohydrates, 5-6 grams of whey protein, 1 gram leucine, 30-120 mg of Vit C, 20-60 IU of Vit E, 100-150 mg of sodium, 60-100 mg of potassium, and 60-220 mg magnesium.
Phase 2: The anabolic phase
This phase is targeted for the 45 minute period directly post workout. The period of enhanced muscle glycogen replenishment and repair and synthesis of muscle tissue. Ingesting 40-50 grams of high-glycemic carbohydrates, 13-15 grams of whey protein, 1-2 grams leucine, 1-2 grams glutamine, 60-100 mg of Vit C, and 80-40 IU of Vit E.
Phase 3: The growth phase
This phase extends from the end of the anabolic phase to the start of the next workout. It can be viewed in 2 segments (first few hours post-exercise and next 16-18 hours) or the rapid and sustained segments. The rapid segment or first few hours post-exercise focus is to maintain increased insulin sensitivity and glucose replenishment. Additionally, this segment speeds waste elimination and tissue repair and muscle growth. The sustained segment maintains a positive nitrogen balance. Growth phase supplement contains 14 grams of whey protein, 2 grams of casein, 3 grams of leucine, 1 gram of glutamine, and 2-4 grams of high-glycemic carbohydrates. During the sustained segment 0.9-1.2 grams of high-quality protein/pound of body weight improves muscle synthesis.
Douglas Paddon-Jones, Melinda Sheffield-Moore, Randall J. Urban, Arthur P. Sanford, Asle Aarsland, Robert R. Wolfe, Arny A. Ferrando; Essential Amino Acid and Carbohydrate Supplementation Ameliorates Muscle Protein Loss in Humans during 28 Days Bedrest, The Journal of Clinical Endocrinology & Metabolism, Volume 89, Issue 9, 1 September 2004, Pages 4351–4358
MacDougall JD, Ray S, Sale DG, et al. (1999) Muscle substrate utilization and lactate production. Can J Appl Physiol 24, 209–215.
McArdle, William D., et al. Exercise Physiology: Nutrition, Energy, and Human Performance. 8th ed., Wolters Kluwer Health/Lippincott Williams & Wilkins, 2015.
Robergs, R. A., Pearson, D. R., Costil, D. L., Fink, D. D., Pascoe, M. A., Benedict, C. P., Lambert, C. P., and Zachweija, J. J. (1991). Muscle glycogenolysis during differing intensities of weight-resistance exercise. Journal of Applied Physiology, 70, 1700-1706
Haff, G. G., et al. 1999. The effect of carbohydrate supplementation on multiple sessions and bouts of resistance exercise. Journal of Strength and Conditioning Research, 13, (2), 111-7.