How Much Muscle Can You Build Naturally? NEW STUDY

Chapters:

00:00 Intro

00:20 1995 Study

00:50 Pre-steroids era Mr. America FFMIs

01:30 2026 Study

02:31 Natty max and Normal distribution

04:04 FFMI for Women

04:31 Body fat % and Frame size

05:25 Conclusion

06:51 Outro

Transcript:

Fitness lore says that for men our maximum muscular potential is a fat-free mass index of 25. The fat-free mass index is basically the bodybuilding equivalent of BMI, body mass index. It’s fat-free mass divided by height squared. Don’t worry, you won’t have to do any math in this video.

The ceiling of 25 comes from a 1995 paper, which found that none of even their most well trained athletes and bodybuilders that were actually natural exceeded a fat-free mass index of 25. It seemed like a hard limit based on just those data, however, this was based on a convenient sample of just 74 lifters. No matter how well trained they were, it’s very unlikely that the maximum muscular human potential will be found in a sample of 74 people.

What everyone ignored is that the same paper also reported the fat-free mass indices of the Mr. America winners from before steroids were in use. In this sample the average fat-free mass index was actually 25.4, and many of these lifters thus clearly exceeded the supposed limit of 25. In fact, the highest reported value was 27.7 by George Eiferman, the 1948 winner of the Mr. America contest. I would note that 1948 is a little bit sus, but the general consensus among historians is that steroids were only widely in use from about 1950 onwards.

Now, in 2026, and new scientific review has reevaluated the question of what the natty max actually is for both men and women. They found that in drug tested athletes fat-free mass indices well over 25 have been reported in multiple papers. In fact, the highest purported value was 31.7, with the 97th percentile being 28.5. Personally, I’m very skeptical of these new data because drug tested does absolutely not mean lifetime natural. We recently saw how “The Juiced-up Olympics” basically failed to beat all of the limits from the supposedly natural Olympics, or at least the drug tested Olympics, and as an industry insider, I can tell you that being doped is not the exception, but it is absolutely the norm. In fact, it’s widely known among athletes, and it’s a statistical fact in a large sample that if you want to be the top of the top of the top, you have to do everything right. “Right” being in this case, everything that it takes to build muscle mass, and that includes doping.

My skepticism of the new data aside, if we combine the new data with the old data from Mr. America winners, especially those from the 1930s, who are almost surely natural, natty max estimate of 28.5 is not unreasonable. However, it’s important to realize that these data are probabilistic. Our natty max follows a normal distribution. That means that in this case, what the researchers called our natty max is the 97th percentile. This does not mean it’s an absolute limit. In fact, it means, by definition, that about 3% of individuals could conceivably exceed this limit, even 28.5. Genetic outliers are a real thing. At the same time, it also means that us mortals with average genetics, or around 50 percentile genetics, can only expect a fat-free mass index of about 23, based on the researchers data. Genetics can make an absolutely monumental difference, even larger than the effect of steroids in many cases.

By social media standards our factory mass index of 23 might seem paltry, a true disappointment for the end of your fitness journey. However, if you’re lucky, you’ll end up looking like Steve Reeves. Esthetics legend Steve Reeves actually had a fat-free mass index of only 23. So if you’re lucky, and you have God tier bone structure, you’ll look like him. If you’re less lucky, you’ll look like me. My fat-free mass index in contest shape was 23.6. I do suspect Steve’s fat-free mass index was actually closer to 25, because his body fat was tested by calipers, but then again he wasn’t that lean. And we know that as you get leaner, your fat-free mass index potential decreases.

For the ladies, I suspect I have better news. The natural maximum muscular potential of men and women seems to be the same, at least in relative terms. However, women obviously start off with around 30% less fat-free mass index. That means that their natty Max is not 28.5, but 23.5, with most women that have more average genetics ending up closer to 20.

If you’re interested what your drug-free maximum muscular potential likely is, I’ve made a calculator for you on my website. The calculator relies on two key inputs. Based on research, there are two clear determinants of your natty max: your body fat percentage and your frame size.

Body fat percentage is commonly ignored in these discussions, and also in the research on the new athletes having a fat-free mass index, sometimes over 30, these are often American football players that are much higher in body fat level. Sumo wrestlers, in fact, have some of the highest fat-free mass indices that we see in the literature. However, they don’t look that muscular because they’re also quite fat.

The cleanest comparison, and therefore the most reliable estimate, is when you are in contest shape, or at least the contest shape of the Mr. America winners from the 1930s and 40s. Skeletal frame size is also incredibly important. Your skeletal frame size functions essentially like a coat rack that determines how much clothes you can put on the frame, or in our case, how much muscle you can put on the skeleton.

Now, before you use the calculator a word of warning. Most people want to know their natty max for the wrong reasons. They want to see if someone is natural, or they want to see how they do in comparison. It’s like a school when someone asks: “How did you do on your test?” Most people aren’t actually interested in how the other person did. They’re interested in how they did in comparison. But comparison is the thief of joy.

What research finds is that when you have a performance mindset or a goal relative to someone else, that often doesn’t lead to long term happiness. Instead, what you want is a growth mindset. In our case, literally a growth mindset in terms of muscle growth, but also psychologically a growth mindset in terms of self-improvement, personal development. You want to be better than you were before. So all that really matters is where you were before, where you are now, and that you are moving in the right direction.

These are the things that ultimately matter for you, not so much how muscular someone else is, because that is outside of your control. So it is best to focus on your own development and to see your natty max estimate merely as a rough guideline of where you could possibly end up at, with the most actionable implementation of that being how advanced you currently are. It gives you the best estimate of whether you are currently a novice, intermediate, or advanced lifter, which actually has implications for how you should train.

Beyond that, it is mostly just a number that doesn’t actually change what you should be doing to get more muscular and leaner. All that said, the link to the calculator should be popping up on your screen right about now, and you can also find it in the description. I hope this video helps you with your fitness journey.

See you next time!