Do We Really Need High Amounts of Carbohydrate for Muscle Growth?


Foods such as pasta, rice and porridge oats are high in carbohydrate. A high daily intake of carbohydrate can be advantageous for endurance training.

However, resistance exercise (weight training) is metabolically very different from endurance training. It results in a completely different muscular adaptation.

Typical recommendations for someone looking to gain muscle mass are currently between 3 and 7g of carbohydrate per kg of body mass. For someone weighing 70kg that works at between 210 and 490g of carbohydrate per day.

Do we really need that extremely high amount of carbohydrate in the diet?

This high amount of carbohydrate may not be necessary to ensure optimal muscle growth. Carbohydrate intakes less than the current recommendations does not decrease performance during resistance exercise.

The cellular responses responsible for muscle growth are not weakened by a carbohydrate intake lower than these recommendations.

Muscle Glycogen and resistance exercise

Carbohydrate is stored in the muscle in the form of glycogen. A single weight training session can reduce your muscle glycogen store (carbohydrate stores) by approximately 25-40%.

Muscle force production during resistance exercise relies heavily on energy production from the breakdown of phosphocreatine and muscle glycogen.

Therefore, if we are using up some of our fuel stores during exercise, there is a need to refuel (consume carbohydrate).

Can the body refuel itself without the need of high amounts of carbohydrate?

A research study measured the content of muscle glycogen before, immediately after and 2 hours after a weight session. This study looked at the content of muscle glycogen if no food was consumed in the hours after a weight session.

The study found that immediately after the weight session, muscle glycogen decreased to 61% of pre-exercise values. However, 2 hours after exercise, muscle glycogen content increased to 79% of pre-exercise values, without the provision of food.

This shows that the body can increase its fuel stores without an incoming source of carbohydrate. Therefore to allow muscle glycogen stores to return to their 100% capacity, is an extremely high level of carbohydrate necessary?

Does a HIGH level of carbohydrate improve resistance exercise performance?

Research also shows, that increasing the carbohydrate intake in the diet from 40% of dietary intake to 60% of dietary intake has no significant effect on muscular strength or endurance

Following 30 days of a ketogenic diet where carbohydrate intake accounted for 5% of dietary intake, research shows that muscular performance and endurance is maintained.

Does a HIGH level of carbohydrate improve post-exercise muscle growth?

A high intake of carbohydrate results in the release of insulin from the pancreas. An increase in insulin release is necessary for muscle growth. However, an increase in insulin levels, as a result of carbohydrate intake, does not affect muscle growth.

When protein alone is ingested, insulin levels increase enough to assist in the making of new muscle. Carbohydrate is not required to increase levels of insulin to concentrations necessary for muscle growth. When carbohydrate and protein are ingested together post-workout, there is no additional benefit to muscle growth than when protein is ingested alone.

Insulin only provides a helping hand when it comes to muscle growth. Insulin's effect on muscle growth is only significant when a sufficient amount of amino acids are present.

Does Carbohydrate have “muscle sparing” abilities?

It has been claimed that carbohydrate may have muscle sparing abilities, through the suppression of muscle protein breakdown. However, when carbohydrate and whey protein are ingested together, there is no difference in muscle protein breakdown compared to when protein is ingested alone.

Research also shows that a lower carbohydrate diet does not impair the cellular response to resistance exercise and has no detrimental effect on muscle growth post workout.

In conclusion, Research suggests that low levels of muscle glycogen has a minimal effect on muscle growth. The effect of adequate daily protein intake, in combination with a well-formulated training routine is sufficient enough to promote muscle growth, irrespective of carbohydrate intake.

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