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Is there a limit to the anabolic response to a high protein meal?

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Is there a limit to the anabolic response to a high protein meal?

I have previously explored the theme of protein intake and frequency and how it can affect muscle protein synthesis. I suggest the optimising nutrition series of articles for a look at some of the past work on this area.

Old School Bodybuilding  - The more protein the better

Today in the bodybuilding world there is a furious debate concerning not just protein frequency but the limits beyond which further protein consumed ceases to be of benefit. Traditionally, most people in the strength sports have assumed that more is better when it comes to protein intake which has led to the espousal of truly ridiculous levels of protein by some of the bodybuilding elite who dominate the Mr Olympia contests. Consuming 2g of protein per pound of bodyweight is considered low by those who adopt this view with the most hardcore athletes swearing blind that any less than 600 grams of protein a day is just playing around. Inevitably, the copious use of performance enhancing drugs by these athletes is overlooked and many a trainee has assumed that they should follow the nutrition plans of the pros and expect to get the same results. When their results fail to match their dreams, frustration is the only outcome. Surely there is a better way?

Less frequency, less protein

It was against this background of bodybuilders advocating upwards of 10-12 meals a day and huge protein intakes, that many decided to take an interest in the science of protein in more detail. Once we look at the science it has been noted by many that protein intakes of around 30g tend to maximise muscle protein synthesis – that is, the rate at which new muscle tissue is formed. As a consequence of this, many decided that eating beyond this was a waste of time and we have seen a great many people adopting this viewpoint in recent years. This school of thinking tends to believe that eating no more than one gram of protein per pound of bodyweight is more than sufficient based on the science.

The rise of Martin Berkhan

I first corresponded with Martin Berkhan several years ago, around 2006-2007. At the time his leangains theory was considered extremely radical and even the members of the Body Recomposition website run by Lyle Mcdonald would question his methods in detail. Berkhan’s approach when you boil it down to its essence advocated a period of fasting every day with a 16hr period without food alternated with an 8hr eating window. During the fast you would eat nothing, although minimal calories in the form of black coffee or some EAA’s was permitted. During the feasting phase of the day the adherents of leangains were consuming prodigious quantities of food, with many peoples’ final meals of the day containing 2000+ calories easily and with protein intakes in that final meal closer to 300 grams than 30 grams.

Is there a dose beyond which further protein has no effect?

Authorities such as Layne Norton (see our interview with Layne), have postulated the theory that the protein synthetic response to a meal is determined by the BCAA content, or more specifically, the leucine content of a meal. Layne’s theory states that consuming a greater amount of protein than that which maximally stimulates muscle protein synthesis is a waste. As we can see from the brief overview presented, the subject of protein intake is one that never ceases to bring forth different opinions depending on who is asked. Recently though there has been a new paper in this field which may help to settle some the arguments, at least temporarily. Robert Wolfe and Nicolaas Deutz[1] recently sought to tackle this question in what is likely to turn out to be a landmark paper.

Research Review – Is there a maximal anabolic response to protein intake with a meal?

The scientists opened their research by accepting that the research to date has shown that protein intakes of 20-30g have been shown to maximally stimulate protein synthesis. Most such studies have failed to examine muscle protein anabolism, that is they have failed to measure protein synthesis minus protein breakdown. Furthermore, the authors state that the bulk of prior research has been conducted on amino acid solutions or isolated proteins. Wolfe and Deutz proposed to measure the muscle protein anabolic response and to do so both using isolated protein or amino acid intakes and again when protein is consumed in a meal along with additional nutrients such as carbohydrates and fats.

The researchers speculated that while protein synthesis can be “maxed out”, further increases in protein intake could act as a signal to limit the rate of protein breakdown. If less protein is broken down the end result is that people will gain more muscle, not because they are stimulating great muscle gains by consuming more protein but by limiting the loss of muscle. In bodybuilding jargon, protein’s anti-catabolic effect would be responsible for increased muscle size in this scenario. With the impact of the hormone insulin also having a powerful anti-catabolic effect, the greater protein consumed is likely to be even more anti-catabolic at higher intakes.

Is there an upper limit to the anabolic response to protein intake with a meal?

The theory described by the researchers would suggest that increasingly higher intakes of protein should have a positive effect on muscle gains as the greater protein and insulin levels causes a potent anti-catabolic effect which limits muscle breakdown leading to greater muscle anabolism.

Relation between the intake of essential amino acids (represented by the phenylalanine intake) and net protein synthesis after a bolus meal with a protein mixture with added carbohydrates in a group of male and females between 45 and 70 years of age. All data are expressed per kg fat-free mass (ffm). Between 240 and 330 μmol phenylalanine is present in 1 g protein. With an average of about 50 kg of ffm/subject, 100 μmol phenylalanine/kg ffm represents about 15–20 g of protein in the bolus drink. Based on the results demonstrated above, Wolfe and Deutz conclude that: “It is important to note that in all studies in which net protein synthesis has been measured, the relationship between amino acid availability and net gain is linear, with no plateau of effect at higher levels of availability. From these data we must conclude that there is no practical upper limit to the anabolic response to protein or amino acid intake in the context of a meal.”

Our Comments

The normal dinner usually contains 30+ grams of protein in Western societies with evening meals comprising the bulk of the daily protein intake for most non-training people. With the acceptance of the 30 gram limit to protein accepted by the majority of nutritionists and bodybuilders, it has led most athletes to evenly distribute their protein intake throughout the day with frequent feedings of 30 grams of protein at a time with the intention of maximally stimulating muscle growth. This approach assumes that the goal of protein intake is maximally stimulating protein synthesis, however, the researchers demonstrate in this paper that when it comes to the total anabolic response to protein intake, an increased protein intake and the influence of a complete meal which triggers greater insulin release will combine to boost muscle growth more than a focus on just protein synthesis. Wolfe and Deutz explicitly state that “In our opinion…evidence indicates that the more protein in a meal, the more anabolism will be observed”. What this study demonstrates is support for those people practicing forms of intermittent fasting such as Berkhan’s Leangains method at least in so far as Berkhan argues vociferously for much higher protein intakes at dinner than is commonly seen by mainstream nutritionists. At the same time, the old school bodybuilders whose approach is eat as much protein as they can stomach, can now claim that their consumption of excessive amounts of protein has some backing in science as they are helping to build greater muscle mass by lowering their rate of protein breakdown.

Key Points

  • While there is support for the 30g of protein per meal it fails to look at the bigger picture
  • Greater protein intake leads to less muscle breakdown which can lead to greater muscle gains than a focus on aiming to have around 30g of protein per meal.
  • Evidence suggests that the more protein you eat, the greater the amount of muscle gained; there appears to be no tapering of effect at higher levels based on the research to date.
  • Consuming protein alongside carbohydrates will amplify the effect by releasing the anti-catabolic hormone insulin. More insulin = less muscle breakdown.

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References:

[1] R Wolfe and N Deutz (2012): Is there a maximal anabolic response to protein intake with a meal?