When it comes to gaining or maintaining muscle mass, I think everyone has the general idea that the most important contributors to success are: 1. eating enough protein and 2. Doing some sort of resistance training. But what is the relative importance of each of these? If we HAD to choose between getting enough protein or lifting, which one would give us the best outcome for gaining muscle? I realize I am creating a false dichotomy here, and that an ideal situation would involve both sufficient protein and a solid lifting routine. However, thinking about it as a zero-sum game forces us to think about exactly how important each one is to our goal in a way that a “just do everything right” approach might not. After all, people have a finite amount of time and energy to think about and implement these things, so it is important to really think deeply about what is actually contributing the most to what we want.
In this article, I am going to be making the case that providing a stimulus to the muscle through lifting is a FAR more important consideration than protein intake when it comes to gaining and maintaining muscle. My position is based on two main points:
- The effect of increased protein on muscle growth is much smaller and less precise than most people think.
- Most Americans are much further behind on resistance training recommendations than they are on protein recommendations.
The effect on protein on muscle growth is small and imprecise
If you were to ask 100 evidence-based nutrition or strength coaches what the optimal range for protein intake is, I bet that at least 90 of them would tell you 1.6g to 2.2g per kg of body mass. This has become the standard response in the fitness world, and is widely accepted as truth. This is mostly for good reason. The range initially came from this meta-analysis, which as any good evidence-based coach knows is the highest form of evidence we can hope for. And while I have no issue with people recommending that range per se, I think we place a bit too much confidence in the precision of how that range was obtained.
The below graph from the meta-analysis shows exactly how this range was determined.
It plots total protein intake against changes in fat-free mass in several resistance training studies. From that, the researchers did something called a breakpoint analysis, where statistical software searches through the data looking for a protein intake at which further increases do not reliably cause increases in fat free mass. Basically, at what point does more protein stop reliably causing more muscle growth. In this analysis, 1.6g/kg was identified as that number.
Now here’s the part that most people do not discuss. See that horizontal bi-directional arrow down at the bottom? That is a 95% confidence interval, and it stretches from 1.03g to 2.2g. Essentially the way to interpret this is that, statistically speaking, the true breakpoint is just as likely to be ANY number in that range, 1.6 just happens to be the midpoint. This means that it is just as plausible that any additional protein past the 1.2g mark, for instance, does not cause increased muscle growth. Another way of interpreting this is that it is not entirely clear that individuals consuming 1.2g of protein per day are any worse off than those consuming 2.2g per day.
There have been several other studies that have identified breakpoints very close to the 1.6g/kg mark, but they all also have pretty wide confidence intervals (most bottom out around 1.2g/kg). The point that I am trying to make here, is that even pretty large differences in protein are unlikely to have a very big effect on muscle growth, especially the higher you get on the intake spectrum. For example, if an 80kg person were to try and increase their protein intake from 1.2g per kg (96g) all the way to 2g per kg (160g), the additional 64g of protein might require a pretty significant amount of effort to achieve, and based on the data available it is not clear that it would produce a significant benefit.
To be absolutely clear, protein intake is important for muscle growth. However, the thought that you are leaving massive gains on the table because you are eating a measly 1.4g/kg of protein versus 2.2g/kg is not supported by the evidence. More probably is a little better, but the difference is so small that it is undetectable in even these larger meta-analyses. Which leads into my last point, when we are deciding what sort of things we put time and effort into thinking about (or creating public health policy about), what should we really be focusing on? To me, it should be the thing where the largest gap exists between the current state of things and the ideal state.
Most Americans are much further behind on resistance training recommendations
When looking at the general population, protein intakes tend to fall between 1.1g and 1.2g per kg of body weight. Taking that in context with what we’ve discussed above, most people really are not that far off from optimal levels of protein to support muscle growth. Resistance training is another story.
The current physical activity guidelines recommend at least two days per week of full body resistance training, which I am sure sounds relatively low for this audience. Even then, only about 31% of Americans are meeting that goal. Which means over two thirds of Americans are doing less than TWO resistance training sessions per week.
When we compare the gap between ideal and current state of affairs in these two scenarios, it is clear that we have much more work to be done when it comes to promoting resistance training. Additionally, think about the impact that closing each gap would have. Going from 0 to 2 resistance training sessions per week has the potential to add several years to someone’s health span, whereas increasing protein intake from 1.2g/kg to 1.6g/kg might just let you increase muscle mass at an imperceptibly faster rate.
Take Home Message
I again want to emphasize that I do think that getting enough protein is absolutely important for muscle growth, but the magnitude and precision of effect of specific protein targets are not as rock solid as many think. If you are just a normal person trying to live life and support your recreational lifting activities, and moving from 1.4g/kg to 2g/kg of protein causes a significant stressor or detracts from the enjoyment of your goal dietary pattern (and therefore likely adherence), it is not worth it to continue pursuing that higher target. Let’s not forget that every calorie spent on one macronutrient is a calorie that cannot be spent on another. And if you are displacing some delicious carbs or fats because of the belief that you MUST have that extra 50g of protein in your diet to see progress, rest assured that you are probably going to be just fine taking some protein away.
I also want to note that this article was focused solely on protein’s effects on muscle growth, but there are plenty of other reasons somebody might want to eat more protein. Protein tends to more satiating, for example, and that may help someone attain a calorie intake that is appropriate for them. You could also just like protein-rich foods. Both are valid reasons to pursue higher intakes of protein. But when it comes specifically to muscle growth, it is not the make or break factor for most people.
