Understanding What Does and Doesn’t Drive Muscle Growth
The model of muscle growth is poorly understood by the average person as is, but many professionals don’t come close to understand it either.
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Sometimes I come across popular ideas in nutrition that can’t possibly be true despite being so enforced by many industry figures I look up to. That being said, I know nobody is infallible, not even credible coaches and researchers, so while it’s risky to disagree with the majority, I think we can all agree that discovering the truth is most important.
Where am I going with all this?
Well, many science-based coaches have been overly promoting this idea that more protein is better for body composition. More specifically, the claims that I want to tackle today are the following:
These ideas stem from a few published studies done by deeply credible researchers, so if you don’t look into the deeper details of science as a whole, it’s easy to regurgitate the same questionable conclusions everyone else is saying.
The lead researchers of the popular studies I’m questioning are Jose Antonio and Bill Campbell, both of which I usually agree with.
Mainly, I disagree with the common interpretation of these topics regarding a few of their studies. I mean no disrespect to them personally, despite how passionately I might press into some points. Let’s start with the first claim.
Antonio et al conducted a set of studies looking at very high protein intakes, the kind of intake that would make your local butcher rich.
The first study compared a low protein group of 1.8 g/kg/day to a high protein group of 4.4 g/kg/day in trained lifters (1). 4.4g/kg/day is 2x your bodyweight in pounds per day, so a 200 pound person in this study would have to eat 400 grams of protein daily. Both groups were instructed to eat their baseline diet while the high protein group was instructed to eat more protein to reach their target.
After 8 weeks, both groups kept the same body composition with no statistical difference despite the high protein group reportedly being in an 800 calorie surplus along with eating more carbs and fat.
The second study similar in design, compared a low protein group of 2.3 g/kg/day to a high protein group of 3.4g/kg/day in trained lifters (2). The high protein group had a 300 calorie bigger surplus along with also eating more carbs and fat.
After 8 weeks, both groups statistically recomped. The low protein group gained more weight while the high protein group kept the same weight. The high protein group also lost more fat, so they essentially had better recomp results.
The third study, compared a low protein group of 2.6 g/kg/day to a high protein group of 3.3g/kg/day in trained lifters (3). The high protein group ate about 400 more calories daily. After 4 months, both groups had no significant body composition changes with no differences between groups.
At first glance, these studies make it look like protein is impossible to be fattening even in a caloric surplus. Many coaches will interpret it this way and end up posting contradicting content. They’ll make one post about any nutrient in a surplus causing fat gain, while the very next day, they’ll make a post about how overeating protein can’t make you fat. C’mon bro.
Mechanistically, we know a surplus of protein can cause fat gain (4,19). While it’s true that the excess protein itself rarely turns into actual fat, the excess will be oxidized for energy leaving less carbs/fat to be burned off resulting in more of those nutrients getting stored as fat (5).
In essence, physiology doesn’t give you any free passes. Any excess of energy will result in stored fat after muscle building limits are maxed out.
This means for protein to be as magical as the Antonio studies suggest, it must have energy expending effects powerful enough to burn off all the additional calories you ate from extra protein along with the additional carbs/fat consumed in all 3 high protein groups.
The proposed explanation by the authors was a combination of an increase in exercise expenditure, NEAT, and the thermic effect of food (TEF).
Exercise expenditure couldn’t have made a difference because both groups did the same training program with the same volume. In fact, in the first study, there was a noticeable trend for the lower protein group doing and gaining more volume load. It’s also important to note that in these studies, the workouts were unsupervised which is another limitation to consider.
Furthermore, in all 3 studies, no group significantly gained more muscle or performance, so there is nowhere to point to for protein causing additional exercise related expenditure.
That brings me to the next point. NEAT.
NEAT stands for non-exercise activity thermogenesis. It’s just a fancy word meaning the calories you burn from non-formal exercise like blinking, brushing your teeth, or double tapping a picture on the gram. I don’t know of a single study showing protein as a sole variable increasing NEAT, let alone to any meaningful degree.
Moreover, we do certainly know NEAT more likely decreases with weight/fat loss. In the second study, the high protein group lost more weight than the low protein group, so this is a stretch to claim NEAT skyrocketed to a jawdropping rate.
Lastly is TEF which is how many calories you burn from digesting food and it’s the weakest way our body burns calories leaving more skepticism. Protein does have the highest TEF when compared to carbs and fat (6,7).
However, this is only in isolation and is at most 20-25%. When eaten within mixed meals, even with triple the protein content, the thermic effect is not different or enhanced (8,9).
There is also no additional TEF benefits to overfeeding long term with excess protein (10). Even if there was, for the Antonio studies to be plausible, TEF would have to exceed 100% to negate all the additional protein calories along with the extra carbs/fat consumed by the high protein groups. If this were the case, extremely high protein diets would be the new miracle diet that cancels out all calories more magical than any spell taught at Hogwarts.
Long story short, even in combination, the 3 most feasible explanations falls considerably short. And without these explanations, you have to impossibly defy the laws of thermodynamics in order to get the mind blowing results seen in the Antonio studies.
The culprit that explains these radical results are simple. Self-report. Despite the subjects being trained lifters, humans are notorious for making errors and self-reporting data is often concluded to be deeply unreliable (11).
Oftentimes, university studies involve subjects as mutual friends which naturally comes with social, personal, and physical expectations/incentives. In other words, you don’t want to be known as that guy that drops out of the study. You’d rather stick it out for numerous reasons even if it means not fully adhering to the difficult requirements whether intentionally, subconsciously, or mistakenly.
The studies had pretty high dropout rates as is. One can only assume how difficult it must be for the remaining participants in the high protein groups to reach 3.3-4.4 g/kg/day of protein without compensating their normal diets for 2-4 months straight. If done with the prescribed protocol, it should feel like withstanding the discomfort of eating a giant meat buffet except you have to tolerate it again and again for months without breaks. Good luck with that.
A different lab replicated a similar study in trained lifters, but didn’t get congruent results with Antonio (12). Although they also involved self-reporting, they had a more doable protein target for the high protein group. This study overfed 2 groups with diets equal in calories. One group had a protein intake of 1.1g/kg/day compared to a high protein group of 2.5g/kg/day.
Both groups gained the same amount of fat. Even with the low protein group eating a very suboptimal dosage, the high protein group doubling their protein intake didn’t protect from further fat gain in a separate lab.
A 2013 Meta-analysis of 15 randomized controlled trials also supports that additional protein does not particularly protect you from fat gain (13).
Furthermore, Bray et al conducted 2 similar studies in non-lifters using a metabolic chamber (14,15). For those who don’t know, metabolic chambers are rooms that detect and control all the energy in and out. Food is directly fed to subjects, energy is accurately measured, and there’s no need to ponder about the human race making mistakes or misreporting data.
These uber expensive, yet high quality studies compared 5% to 15% to 25% of caloric intake as protein while all groups were overfed a 40% surplus.
In both studies, fat gain was the same between all 3 groups even in the high protein eating about 3 g/kg/day.
Muscle gain was significantly lower in the low protein group, but was the same between the middle and high protein group indicating what some coaches already know to be true. Once sufficient protein intake is met, there’s no additional body composition benefits to more. Eating more doesn’t spare fat gain, increase fat loss nor does it add on more muscle mass.
This brings me to the next study I’m addressing.
In Campbell’s study, if you just read the abstract (synopsis for research papers), you would think more protein is better for recomping (16).
This study compared a high protein intake of at least 2.5g/kg/day against a low protein group with at most 0.9g/kg/day in trained aspiring female physique athletes.
This study designed and controlled the training program very well (kudos for that), but didn’t control for caloric intake, so we have no clue what the energy balance difference was between groups. They also didn’t control for non-muscular water gain which can confound results (18).
The results found the high protein group recomped significantly better by gaining more muscle and losing more fat.
The 0.9 limit in the low protein group is so questionable from a design perspective because that’s such a suboptimal dose for lifters which the authors even addressed in the paper describing it as what average sedentary people consume.
So the interpretation shouldn’t be “more protein increases your odds of recomping or enhances the effects of it.” The interpretation is what I mentioned earlier, there are no body composition benefits to protein beyond an already optimal dose (1.6-1.8g/kg/day) which the authors touched on (17).
In fact, besides the Antonio studies, all the other studies they cited in his paper supports this. As you go from suboptimal protein towards optimal, you get better body composition results, but going past optimal has not been shown to be better.
If that were the case, all you can eat shrimp at Red Lobster would produce some of the leanest most jacked customers ever.
Another confounding factor in this study was protein timing. The high protein group got fed an optimal pre and post-workout protein timing protocol while the low protein group got a suboptimal version which they mentioned as well.
Furthermore, I don’t disagree with the authors that body recomposition can happen in a deficit or surplus along with occurring in trained lifters, I just disagree with the interpretation of more protein enhancing body recomposition.
Once optimal protein intake is achieved, body composition benefits are maximized. Any further benefit or increased odds of recomping would depend on other factors like training, body fat levels, genetics, training experience, etc.
Ultimately, I don’t fault Jose Antonio or Bill Campbell. They’re great researchers who did what they can with their budget and reported the data as follows. That being said, all of us, researchers or not have a responsibility to dissect truth and teach accurate conclusions which I don’t think many coaches are doing when referencing these studies.
Physiologically, it just doesn’t make sense for protein to have these exaggerated effects past an already optimal intake which many fitness enthusiasts are already consuming.
So here are some crucial truths you need to grasp that will challenge some of the common regurgitated advice you hear:
Don’t get me wrong, protein is important for making you look good naked, but once you get enough, eating more doesn’t prevent consequences or speed up results. Period.
Haun, Cody T, et al. “Effects of Graded Whey Supplementation During Extreme-Volume Resistance Training.” Frontiers in Nutrition, Frontiers Media S.A., 11 Sept. 2018, www.ncbi.nlm.nih.gov/pmc/articles/PMC6141782/.
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