Previously, I wrote about the realistic limit for dropping body fat. Why? Because many people approach what can be considered the best natural degree of leanness and feel unfulfilled because they have read of someone, somewhere, with lower body fat. The same happens with muscularity. Now, before any of you go flying off in one direction or the other, I am talking about how much skeletal muscle a person has, though this is rarely measured directly. The best surrogate is calculated fat-free mass or lean mass. This is obtained by taking a person’s mass (weight in kg) and subtracting the percentage that is fat mass as calculated from any of a variety of measures. In the article where I spoke of how lean a person can get in a healthy and drug-free manner, I mentioned that I don’t use age-corrected figures or worry about visceral and organ-associated fat. My concern there related to the target most people have of appearing lean, knowing that other fat stores that are more of a concern in regards to a person’s health also drop (a benefit) while pursuing a physique goal.

Now, in this case, we need to account for the amount of total fat in the body, but again, there are problems. The formulas differ among the various techniques used to measure body fat. Also, they generally are inaccurate at the extremes, meaning people who are very obese and very lean. Further, no study has ever been reported that compared intra-abdominal and organ-associated fat with a person’s life-long habits. In other words, does a person who has always followed a lifestyle of healthy eating and fitness-based recreation have less fat than someone who has only recently achieved a lean physique after decades of decadence? No idea, but you have to imagine that the body does not forgive chronic excess that easily. So, there is some guesswork here, but work with me on the general message.


When Does Most Of The Muscle Mass Get Created?
Most people can agree that for the general public, peak muscle mass likely occurs during a person’s twenties. This is when they are at the peak of production for hormones that promote strength and muscle mass gains; they generally have the luxury of leisure time that can be spent in active recreation (e.g. exercise, sports, etc); and life’s little injuries haven’t tallied up yet. Yes, most people become couch potatoes as soon as gym class becomes an elective in high school, but they will fall on the lower end of the bell-shaped curve. I guess that is fitting as they often become bell-shaped. Also, I am talking about the process that occurs without the aid of anabolic drugs. That is an entirely different topic, with health, ethical, legal, and social aspects that are under-considered in most discussions.


What Does The Research Say?
So, what does research say is the peak muscle mass that can be achieved drug-free? Thankfully, a few studies have looked at this issue and report similar findings. If you want to jump to the bottom of the article for the answer, you won’t hurt my feelings. But if you are interested in how people find these kind of numbers, how they actually apply to reality, and how to explain it to friends when they challenge you, then join me on my little intellectual walk on the path less traveled.

Realizing that bodybuilding is seen as a fringe activity, and most doctors do not see people coming into their clinics complaining of having too much muscle, there have not been any active intervention studies. In other words, conventional doctors and scientists have not attempted to produce Übermensch sports warriors. This did happen in the 1950s through the 1970s in several countries following the “end” of the Cold War, as sports were seen as a way to rebuild national pride. East Germany (yes, Germany was divided after World War II ended, and rejoined about 25 years ago) had a program that was uncovered after extensive records were discovered about a program designed to create the best athletes in the world. Sadly, the program used abusive tactics and androgenic-anabolic steroids, and other drugs in athletes as young as 10 years old. To say this no longer occurs covertly or could never happen in the U.S. is a bit naive. The relevant focus in modern day is rebuilding strength and muscle mass in aging adults. It is closing the barn door after the horse is loose, but that is how grant funding works. There are also observational surveys of drug-free bodybuilders, measuring their fat-free mass. These young men are likely near the physiologic max in terms of muscle mass with a healthy body fat. Though there will be certain individuals who surpass the described limits of peak muscle mass – without the aid of performance enhancing drugs, the information should work for nearly all of us mere mortals.

The reference adult male is about 176 cm tall, and weighs around 70 kg. This gives him a BMI of 23.4, and a fat-free mass index (FFMI) of 19.9 if he has 15% body fat (an athletic level of body fat). If he has 10% body fat, his FFMI is 21.1. If he has the physiologically lowest body fat that can be maintained without affecting health (about 5%), his FFMI is 22.2. So, a person who has what science considered to be the physiologic normal body mass for an adult male can attain a FFMI of around 22 without consciously trying to augment his muscle mass, if he is extremely lean. Now, certain groups do augment (build) their muscle mass for reasons of: athletic performance, job requirements, hoping to become more attractive to potential mates, or as a matter of self-development. These reasons are by no means exclusive. The methods used to build muscle mass seem quite varied if you make the mistake of doing an internet search for “how to build muscle,” but essentially you are talking about resistance exercise combined with a higher than maintenance intake of protein.

Just this year, a paper was published in the journal Osteoporosis International (Frost, et al, 2014) that measured total lean body mass in young men, 20 – 29 years of age, as well as older men, 60 – 74 years of age, to determine defining thresholds for sarcopenia (loss of lean mass due to aging, wasting disease, starvation, etc). We have to tease out the data, but from this sample of young men, the average total lean mass was 64.7 kg, and the top 2.5% had a total lean mass (determined by DEXA) of 78.3 kg. Bear in mind, this was a random sample, not people who exercise or bodybuilders. They screened out those with excessive drinking, use of anabolic steroids, or being treated with glucocorticoids (anti-inflammatory steroids for asthma, arthritis, etc). From this, using the reported average height of 181 cm, this would show that the average young man has a fat free mass index of 19.75, agreeing with the numbers noted earlier of the “reference man.” The most muscular in this group (783 men) had an estimated fat free mass index of 23.9, assuming we use the average height in the calculation. In absolute numbers, only one subject had a total lean body mass over 90 kg (and just barely), the height of this person was not reported.
A paper published in Calcified Tissue International (Gould, et al, 2014 – see the places you have to hunt for data?) reported similar findings. The average subject had a lean body mass of 19.62, with the top 2.5% having an (estimated) lean body mass of 24.36.


So What About Bodybuilders?
Now, those concerned with maximal muscle development are not concerned with what the average Joe is doing. What is happening in the top group? The most practical way to determine this may be to look at the fat free mass index of bodybuilders. Recognizing that many deplete lean body mass while “cutting up” for a contest, it is probably the best model that is readily available. Also, is it worth it to get a point or two in lean body mass index at the expense of carrying a few more points of fat mass?

Well, there was a study that looked at the fat free mass index of drug free bodybuilders and athletes, and compared them to those of anabolic steroid using bodybuilders. Further, the authors of the study also reported on the fat free mass index of Mr. America winners from the “pre-steroid” era of 1939 – 59. I am not certain as to how they verified the numbers used in the historical subjects. Nonetheless, the drug-free athletes had a “well-defined” limit of 25 for the fat free mass index, and the Mr. America winners demonstrated an average of 25.4 for their fat free mass index. One may wonder, were the estimates for the lean mass or height of the “pre-steroid” Mr. America winners inaccurate? Were steroids present in that population, particularly the latter date subjects? Did these men represent those with greater predisposition for muscle mass or training response to exercise? Good questions all. The men who used anabolic steroids commonly exceeded a fat free mass index of 25, in cases even exceeding 30.

A paper (Loenneke, et al, 2012) comparing fat free mass index measures using DEXA versus bioelectric impedance demonstrated findings consistent with the prior reports. Using NCAA baseball players (drug tested athletes), the fat free mass index did not exceed 24. Admittedly, the training protocol and goal for this population of athletes is not to attain maximal mass, so their motivation and training did not encourage them to develop their physiques, rather than promote operational functionality in their sport.

So, armed with this knowledge, what can one reasonably propose as a physiologic limit to fat-free mass in a drug-free male? It appears that the typical person will hit a ceiling in regards to fat free mass index of 25. That said, if the “pre-steroid” Mr. America winners were accurately calculated to have an average fat free mass index of 25.4 – prior to the advent of protein supplements, creatine, equipped gyms, etc; it is possible that the modern day bodybuilder or athlete may be capable of developing an admirable physique with a fat-free mass index that might reach as high as 27. However, this would probably entail the perfect marriage of genetics, training, and diet.
For those of us working to achieve our personal best, knowing what the physiologic limits are will allow us a sense of satisfaction upon reaching the neighborhood of accomplishment, and avoid over-reaching in attempting to force further growth upon a body that has attain “peak muscle mass.”


What Is The Take Home Message?
So, take home message. If you have a fat free mass index of 25, you are near the peak of your potential development. To gain beyond this point will require you to be gifted with the genetic abilities beyond those of the majority, dedicated training, and optimal nutrition and supplementation. Trying to reach a fat free mass index that exceed 27 without the use anabolic drugs is folly. This will result in either frustration that leads to greater temptation in considering anabolic drugs that have significant health, social, and legal consequences ; or in overeating and gaining fat mass in the pursuit of size for the sake of size.

When using the age-adjusted number of my body fat, I am sitting at a fat free mass index of slightly over 26. I believe I am one of those gifted in my ability to respond to training, and have well over thirty years of weight-lifting experience, a diet that promotes my pursuit, access to and knowledge of supplements that aid in building and retaining muscle mass, and have the support of my wife. In a recent conversation with a gym-buddy who is younger than me by about twenty years, we were discussing the evolution in change in training goals. I have found myself wanting to occasionally challenge myself with trying to reach a new PR, or get cut for a photo opportunity, but my main priority has been (for a number of years) to retain the mass and strength I have. I “feel” that my results are floating, kind of like the speedometer of a car that has an analog gauge, where the needle hovers around 130 mph, or whatever the top-end speed of the car is when you are driving with a death wish. If I let up, I’ll lose a bit of size and strength, but if I push any further, the “engine will redline” and that will result in reduced performance or even damage.

I hope this helps others, as I think it would have helped me earlier in my career. Too often, I would overeat, overtrain, and use way too high a load (heavy weights) in my training in the pursuit of greater mass. Find where you are at, realize that college age athletes have fat free mass index numbers ranging in the lower 20s, and that the elite bodybuilders of the historical age became legends with fat free mass index numbers around 25 to 26.

_DSAbout the Author:
Daniel Gwartney, M.D. took the path less traveled and combined his passion for health, fitness, and bodybuilding with the knowledge and experience learned during his medical training. A former world-ranked natural bodybuilder, appearing on the covers of Muscle Media 2000 and Ironman Magazine, and a regular contributor to several of the top bodybuilding and fitness magazines, he provides unique insight into the application of fitness into medicine and medicine into fitness.