When teens read FLEX magazine and other trash body building rags, they get the idea that all they have to do to look like Phil Heath or any other pro is workout really, really hard and take all the supplements the guys promote.

This is a cruel joke that leaves teens poor, depressed, and with low self esteem because after working out for weeks, months or years they start to think that they are the reason they don’t look like the guys in the magazines. They must not be training hard enough, they must have crappy genetics.

The truth is much more complicated than that. For those interested in the science behind what a natural bodybuilder can accomplish, read on.

There is a physiological upper limit to how much muscle a human can gain without the use of steroids, growth hormones, pro-hormones, insulin, etc…

Why Care About FFMI?

Steroid talk is an endless debate. Hit up Reddit, T-Nation or BodyBuilding.com and just about every progress post degrades into steroid accusations. Some cases are pretty clear, but it’s still ultimately unknowable in most.

I’ve been around steroid users. I know what an in-shape person who transitions into using steroids looks like, and I see that in progress posts all the time. If everyone operated honestly and gave full disclosure that would be the end of it. But an infinitesimally small number of people admit to using, even in clear cases. And for me that is a problem. Not that I want to be a vigilante “truth” seeker, but that I want to spread the truth of what a natural bodybuilder can expect.

The fitness industry thrives on selling an image. Unfortunately if you’re going for the fitness model build in your magazine, the only way to get there is with performance enhancing drugs. Not a specific brand of whey protein, nitric oxide preworkout drinks, creatine, amino acids, weight gainers or whatever else you’re being sold. The fitness industry willfully misleads people into thinking the cause for their models’ success is these products, when those products contribute little to nothing to a their physique compared to drugs and diet.

When individuals make progress posts and detail their routine, diet, and supplement use down to the smallest detail but leave out the drugs they’re on, they perpetuate the myth. It leads to more people wasting their money and having the wrong idea about what is achievable and how to achieve it. Ultimately, it leads to people leaving fitness because they feel defeated.

Bodybuilding is about creating illusions. A lot of the sport is angles, lighting, posing, tanning, peaking techniques, etc…  That’s why it’s more accurately an art than a sport. Combine the already illusory nature of bodybuilding modeling with steroid use, and you’ve got people that hardly resemble humans. These images are attached to advertising which says you can achieve the same look. Because of this many men have unreasonably high standards for what is achievable.

It may be argued that people need something to aspire to, I personally believe that aspirations grounded in truth are much more valuable and conducive to long term success than pie-in-the-sky ideals like modern mass monsters. Anyone can look at Ronnie Coleman and be temporarily motivated, but what happens when you work your ass of for five years and never come close?

I can’t solve all those issues, but the first step is educating newcomers to the weight room so they can enter with realistic expectations.

The Fat-Free Mass Index

The gold standard for identifying natural bodybuilders is the fat-free mass index (FFMI). FFMI is defined by the formula (fat-free body mass in kg) x (height in meters)-2. A slight correction of 6.3 x (1.80 m – height) will normalize these values to the height of a 1.8-m man.

Bobby PandurThere was a study that established a gold standard to screen for drug-use among bodybuilders (Kouri et al., 1995), interestingly much of the the data used to tabulate the FFMI was derived from pre-steroid era bodybuilders.

Data was taken from 84 steroid users and 74 non-users first, then all the Mr. America winners from 1939-1959 were added to the analysis. They concluded that a soft upper limit of 25 was appropriate for non-steroid bodybuilders. I say soft, because a few of the pre-steroid Mr. America’s exceeded this value, the highest FFMI value was 28, the average was ~25.

It should be noted that the max FFMI values are based on bodybuilders in contest condition (e.g. 3-5% body fat), for overweight and fatter individuals, the formula loses validity.

Remember, for the FFMI calculation to work, percent body fat, height and weight need to be as accurate as possible.

FFMI Calculator

I can’t embed a calculator here so hit up this one.

Norms for FFMI in Men

  • 16-17 = Well below average (< / – 20th percentile)
  • 18-19 = Average (25-50th percentile)
  • 20 = Above Average (50-75th percentile)
  • 21 = Well above average (75-90th percentile)
  • 22 = Excellent (95th percentile)
  • 23-25 = Superior (Off the charts for normal adult men, but in the top 85-95th percentile for Natural bodybuilders)
  • 26-27 = Some Natural bodybuilders could get to this level (God Genetics)
  • 28-29 = It is possible but very unlikely to reach this level Naturally
  • 30 or above = We can say with nearly 100% certainty that this person is not natural

I’ve always been a fan of classic era 1970’s bodybuilders, preferring their more aesthetic looks over current day mass monsters. What’s interesting though is that Arnold Schwarzenegger at 6’2″ and 235 lbs had an FFMI that was ~28.7, and he was a known steroid user. So, for even the most genetically gifted natural bodybuilder anything close to a classic era Arnold build is all but a pipe dream.

As for modern mass monsters? Phil Heath’s FFMI is an astonishing 35+.


FFMI is an interesting tool for separating natural bodybuilders from those using non-natural means to gain muscle. However, I’m more interested in using the tool personally than policing others. It’s interesting to play with the calculator to see what weights and body fat combos you would need to reach to hit the upper limits of natural bodybuilding. Doing so results in much more realistic goals for the natural bodybuilder (target 25) or those of us just looking for a good aesthetic build (21+).