Determining the optimal protein intake for muscle growth

Natural bodybuilder Cliff Wilson takes a closer look at the so-called "Protein Change Theory" and how you can adjust your current protein intake to match your current level of development.

An examination of protein change theory and the upper limit of protein intake

There is a question that has been asked time and time again over the years by both scientists and lay people alike, and the answer to this question is still not really conclusive. No, this is not a question about the meaning of life? There are more important things to think about. What people really want to know is "How much protein should I eat to build muscle?"

The answer to this question will vary depending on who you ask. I've heard all these answers before. Some say 2.75 grams per kilogram of body weight, others say 2 grams per pound of body weight and then there's the ever popular answer that says you should eat 2 grams of protein per kilogram of body weight. These are drastically different numbers, but where do they come from and which is the right one - who should you believe?

There are many studies that have set out to find out exactly how much protein is needed for optimal growth. Unfortunately, the scientific community has had answers in the past that have been just as varied as the numbers from the bodybuilding community. Different studies show different rates of muscle growth with drastically different levels of protein intake. How can this be?

Well, recent research shows that protein intake is not as clearly definable as many believe. What does this research say about optimal protein intake? The simple answer might just be this...more than you are currently consuming.

Protein Spread and Protein Change Theories

In a recent study review published in The Journal of the International Society of Sports Nutrition, Bosse and Dixon examined protein spread and protein change theories. This is an excellent review that not only provides explanations for the inconsistent results of different studies on protein intake, but also gives insight into the way we should look at protein intake in general.

Protein spread theory states that in studies of protein intake during intervention, there must be sufficiently large percentage differences in protein intake in grams per kilogram of body weight per day between groups for differences in muscle growth and strength gains to become apparent (1).

When studies compare high protein intake to low protein intake, the difference in the amount of protein consumed between the low protein intake group and the high protein intake group is not large enough to show a significant benefit of supplemental protein. This helps to explain some of the inconsistencies in studies of protein intake.

The protein change theory is what the average bodybuilder/exerciser should be most interested in. Protein change theory states that for gains in strength and muscle mass, there must be a significant increase in protein intake from habitual protein intake to protein intake during the study (1). This means that a sufficient variance (protein spread) must be ensured, and it must also be ensured that the subjects consume significantly more protein than before the start of the study.

This review draws data from many different studies and shows that the results are not as chaotic as they may appear at first glance. This review presents the most convincing argument yet for protein spread and protein change theories. I can only warmly recommend everyone to read this review for themselves.

Although both protein spread and protein change theories are significant, I would like to draw your attention to the protein change theory as it has the most relevance in terms of practical applications and also tells us how our bodies respond to protein and amino acids.

The Protein Change Theory

The protein change theory shows that the human body can basically get used to a given amount of protein and that additional protein is needed to further stimulate anabolism. When it comes to protein intake, one cannot simply compare grams per kilo per day. Rather, changes from baseline need to be considered.

For example, let's say we have two completely identical bodybuilders who both weigh 200 pounds (about 90 kilos). Our first bodybuilder has a history of consuming 200 grams of protein per day. Our second bodybuilder has consumed 275 grams of protein per day.

Let's assume that our first bodybuilder increases his protein intake to 275 grams per day. Our second bodybuilder leaves his protein intake at 275 grams per day. As you can see below, both of our bodybuilders consume the same amount of protein. The main difference is that there is a difference in the percentage increase in protein intake - and protein change theory tells us that this is important.

Base protein intake and % increase in protein intake

• Bodybuilder #1 - 200 grams  275 grams 37.5%
• Bodybuilder #2 - 275 grams  275 grams 0%

Although these two bodybuilders are completely identical in every way and consume the same amount of protein, the bodybuilder with the largest increase in protein intake will likely build muscle at a faster rate.

However, there is one thing to note about this example. Even though the first bodybuilder is likely to start growing at a faster rate, it won't stay that way forever. The body will eventually begin to adapt to the higher protein intake and the rate of anabolism will slow down. This explains why people with similar protein intakes have different rates of muscle growth over a period of time. The protein change theory demonstrates metabolic adaptations in pure culture.

Metabolic adaptations

Human metabolism involves a myriad of chemical reactions in the body and is astonishingly complex. Protein Change Theory requires that we take metabolic adaptations into account when determining optimal protein intake. In previous articles and videos I've gone into more detail on the topic of metabolic adaptations in relation to fat loss, but these metabolic adaptations are also a determining factor in muscle growth and protein intake. The body will ALWAYS strive for homeostasis regardless of the circumstances.

One thing that very few people take into account is that the human metabolism is not static. There are many things such as size, age, gender and certain hormones that affect metabolism that are out of our control. Even things we can control such as calorie and macronutrient intake, physical activity and body weight/fat-free body mass cause the body to make changes to the metabolic rate in order to achieve balance. A common belief is that the body acts almost like a bank where we can deposit and withdraw calories. The typical "calorie intake vs. calorie expenditure" argument in relation to fat loss and muscle growth is a perfect example of this view. This reasoning states that we need to consume more calories than we consume to lose weight and that we need to consume more calories than we consume to gain weight.

The truth is that this is only part of the picture. The human body is less like a bank and more like a stock exchange. We can make deposits and withdrawals, but the market is subject to fluctuations related to what is put in and what is taken out, As with the stock market, we would need to consider the status of the market before deciding what to deposit or withdraw. Many people cannot yet understand how protein can be the subject of metabolic adaptations in the body. The general opinion regarding protein is that you simply need to ensure that the body has sufficient amounts of amino acids available to build muscle. While this is true, it's not the whole story when it comes to protein and oversimplifies the role of amino acids and proteins in the body.

Protein and amino acids as signaling molecules

You've probably heard it a million times by now - proteins are made up of amino acids and amino acids are the building blocks of muscle tissue...etc., etc. I've read this phrase a million times in magazines and articles. This is usually where the information about amino acids ends in most articles. This misleads many people into thinking that there is some magical amount of protein that is sufficient or optimal. If amino acids are only used as substrates, then this would lead us to think that you simply need to supply enough substrates to get the job done. However, it doesn't quite work like that.

While it is true that amino acids have long been viewed simply as substrates for protein synthesis, it has recently been shown that they also act as modulators of intracellular signal transduction pathways, typically associated with growth-promoting hormones such as insulin and IGF-1. This means that certain amino acids not only serve as substrates for protein synthesis, but also regulate this process (2). This is particularly true for the amino acid leucine and its regulation of the mTOR pathway. If amino acids are signaling molecules and not simply substrates, then this will make them the subject of metabolic adaptations by the body. The body appears to become less sensitive to the anabolic response of amino acids over time, so more protein will be needed to drive further changes. This means that optimal protein intake is no longer a static number.

Protein synthesis and net anabolism

This is still not the whole story of protein intake. While amino acids act as modulators of protein synthesis, there is a limit to the amount of protein synthesis that can be stimulated, so there must be another way in which protein can signal growth. Several studies have shown that stimulation of the fractional rate of muscle protein synthesis reaches its maximum value with a protein intake of only 20 to 30 grams. (3).

When trying to determine what is best for muscle growth, it is foolish to look only at the rate of protein synthesis. A protein intake that is above the maximum amount needed to stimulate protein synthesis can still be beneficial. A common belief among bodybuilders is that if you consume too much protein at once, the excess amino acids are simply wasted. This is quite silly when you think about it. Before modern times, humans did not have access to a steady supply of protein. Homo sapiens would occasionally kill an animal and then stuff themselves to the limits of their intake with meat.

There was no way to put protein aside and save it for later, our ancestors had to eat it immediately. It would be quite inefficient for the body to waste these amino acids, as days could pass between meals with significant protein content at these times.

Overall muscle growth is not simply the result of protein synthesis. Instead, we need to look at net anabolism. To determine net anabolism, we need to look at both protein synthesis and muscle protein breakdown. Contrary to what you might think, the body is in a continuous state of synthesis and breakdown. When synthesis outpaces protein breakdown, we speak of anabolism and when protein breakdown outpaces synthesis, we speak of catabolism.

Additional protein intake after a maximum rate of protein synthesis has been reached can still increase net anabolism by reducing protein breakdown rather than by further increasing the rate of protein synthesis. When protein is consumed in large amounts, the rate of protein synthesis begins to increase - but only up to a certain point. Once the maximum rate of protein synthesis has been reached, intracellular amino acid levels will begin to rise.

If protein intake continues to increase, overall anabolism will continue to increase without a corresponding increase in protein synthesis rate. This response appears to come about because the continuous increase in intracellular amino acid levels sends a signal to the body that it should limit the rate of protein breakdown (4).

The reason this signal reduces protein breakdown is believed to be based on the action of insulin and has no upper limit, as protein breakdown continues to decrease with each increase in protein intake (5, 6). This occurs with a single protein meal, so it is realistic to assume that this applies to every protein meal throughout the day. This not only shows that additional daily protein intake will lead to muscle growth, but also that there is no upper limit to how large a single serving of protein can or should be. In other words, anyone who says you can't consume more than a certain amount of protein during a meal is wrong.

Key messages and implications

The Protein Change Theory provides some interesting key messages and implications regarding protein intake. Let's examine the three most important key messages from this new research.

There is no upper limit or maximum amount of protein above which further increases in protein intake will not lead to further growth

We know that there is no realistic upper limit for protein intake during a meal or a day. We need to move away from the idea that there is a maximum amount of protein that is beneficial within the body. Protein intake and its effects on muscle growth are dictated by how much protein is consumed in the moment and how much protein is added to that baseline. This means that additional protein will most likely stimulate additional growth and there seems to be no point at which this is no longer true. BUT this doesn't mean you should immediately start with 600 grams of protein per day, which brings me to key message number 2.

Protein intake needs to be kept high, but adapted to your individual metabolism.

The Protein Change Theory shows that there is no fixed optimal protein intake that is right for everyone. This means that there is no magic amount of grams of protein per kilogram of body weight that could be used as a scheme for everyone. Although on the surface it may seem like more protein is always better, this is not necessarily the case. It is important to keep in mind that nothing in human metabolism is isolated and that everything works in relation to everything else. Different people will have different macronutrient requirements and it is important to remember that carbohydrates and fats have their own benefits in terms of performance. If protein intake is too high, then carbohydrate and fat intake must be kept unacceptably low to prevent calorie intake exceeding calorie needs.

In the long run, this will ultimately hinder muscle growth. On the other hand, if protein intake is set too high without simultaneously reducing carbohydrate and fat intake, calorie intake will rise above requirements, resulting in a sharp increase in body fat levels.

People with an endomorphic body type will require a much different macronutrient composition than those with ectomorphic qualities. So the goal for each metabolic type should be to consume as much protein as possible without exceeding your calorie needs and without compromising the necessary intake of other macronutrients.

I realize this is quite vague, but learning a little more about individual metabolism is not an easy process. When I work with clients, it can take several weeks for them to really know their metabolism.

Protein intake may need to be slowly increased over the course of a bodybuilding career If the protein change theory is true, then the implication is that a trainee's average protein intake should be increased over time. Since the body appears to become less sensitive to the effects of amino acids over time, it would be plausible to consume higher and higher amounts of protein to continue to stimulate growth.

However, this does not mean that you should consume 1000 grams of protein when you are in your fifties. An increase in protein intake should not interfere with the intake of other necessary macronutrients, but a slight increase in average protein intake over the course of a bodybuilding career might be a good idea.

And what next?

It should be noted that there are many other factors regarding protein intake that influence muscle growth. These include the protein sources chosen, the timing of protein intake and the amino acid composition. These topics open the door to other complex processes that could be the subject of separate articles. For now, we can use the new information to adjust our protein intake accordingly. Plenty more research is needed, but our knowledge of protein and amino acids has grown dramatically over the last few years. The protein change theory is still a relatively new idea and the details are not yet fully known, but ideas like this could help us better understand protein intake as a whole. Each new discovery makes things clearer for those of us in the bodybuilding world. Who knows, maybe in a few years we will know everything there is to know about protein and amino acids. Then we can finally address the question of the meaning of life.

References

1. J. Bosse, B. Dixon. Dietary protein to maximize resistance training: a review and examination of protein spread and change theories . J Int Soc of Sports Nutr 2012, Published: September 8, 2012
2. S.R. Kimball, L.S. Jefferson. Role of amino acids in the translational control of protein synthesis in mammals. Seminars in Cell and Developmental Biology; 2005 Feb; V. 16 Issue 1, p. 21-27
3. Symons TB, Sheffield-Moore M, Wolfe RR, Paddon-Jones D. A moderate serving of high-quality protein maximally stimulates skeletal muscle protein synthesis in young and elderly subjects. J Am Diet Assoc. 2009 Sep;109(9):1582-1586PubMed PMID:19699838. Pubmed Central PMCID: 3197704. Epub 2009/08/25. Eng
4. Wolfe RR, Miller SL. Amino acid availability controls muscle protein metabolism. Diabetes Nutr Metab. 1999 Oct;12(5):322-328PubMed PMID: 10741346. Epub 2000/03/31. Eng
5. Pennings B, Groen B, de Lange A, Gijsen AP, Zorenc AH, Senden JM, et al. Amino acid absorption and subsequent muscle protein accretion following graded intakes of whey protein in elderly men. Am J Physiol Endocrinol Metab. 2012 Apr 15;302(8):E992-E999PubMed PMID: 22338070
6. Elango R, Humayun MA, Ball RO, Pencharz PB. Protein requirement of healthy school-age children determined by the indicator amino acid oxidation method. Am J Clin Nutr. 2011 Dec;94(6):1545-1552PubMed PMID: 22049165