A new study found that bodybuilders using anabolic steroids had significantly larger hearts, livers, kidneys, and spleens than natural athletes. Here's what the research says—and what it could mean for your health.
Most people understand that anabolic steroids can dramatically increase muscle mass. That's the whole reason many bodybuilders and athletes use them. But muscles aren't the only tissues in the body that respond to anabolic drugs.
A question researchers have been trying to answer for years is whether steroids can also cause your internal organs to grow—and if so, whether that growth could create serious health problems.
The answer may be yes, according to a new study published (online ahead of print) in Medicine & Science in Sports & Exercise, the official journal of the American College of Sports Medicine (ACSM).
Here's what you need to know...
If you've followed professional bodybuilding over the last couple of decades, you've probably noticed competitors with unusually distended midsections despite carrying extremely low levels of body fat. Some call it "bubble gut," the medical term for it is visceromegaly, which simply means enlargement of the internal organs. Exactly what's responsible for that enlargement has remained a matter of debate.
Three main theories have emerged over the years.
Some have argued that bodybuilders simply consume so much protein that their organs adapt by growing larger. Others have blamed the widespread use of growth hormone, which is known to stimulate tissue growth throughout the body. A third theory is that anabolic steroids themselves are responsible.
Until now, however, there hasn't been much evidence clearly separating those possibilities.
To investigate, researchers recruited three groups of men: 15 competitive bodybuilders who regularly used performance-enhancing drugs (PEDs), 15 drug-tested natural bodybuilders, and 15 recreationally active men who served as controls.
Using MRI scans, they measured not only skeletal muscle but also the size of several major organs, including the heart, liver, kidneys, and spleen.
The results were difficult to ignore. The natural bodybuilders had organs that were nearly identical in size to the recreationally active controls. The enhanced bodybuilders, on the other hand, had hearts, livers, kidneys, and spleens that were as much as 52% larger than those of both comparison groups.
In other words, lifting weights and building an impressive physique alone didn't appear to enlarge the organs. The dramatic differences were seen only in the athletes using PEDs.
One of the most interesting findings involved protein intake. Both groups of bodybuilders reported eating virtually the same amount of protein—about 1.25 grams per pound of body weight per day (ie, 250 grams for a 200-pound individual). If high-protein diets were driving organ enlargement, you'd expect both groups to have similarly sized organs. They didn't, making protein intake a very unlikely explanation.
Growth hormone (GH) doesn't appear to fully explain the findings, either. Although GH has long been associated with organ growth, only about 20% of the enhanced bodybuilders reported using it. Yet enlarged organs were found throughout the entire enhanced group, including those who used anabolic steroids without GH.
These resutls strongly suggest that anabolic steroids themselves are playing a significant role.
Does that mean every person who uses steroids will develop enlarged organs? Not necessarily.
This study wasn't designed to determine how much steroid use is required, how long someone has to use them, or whether certain drugs pose a greater risk than others. Those are questions future research will need to answer. But the findings do provide some of the strongest evidence to date that anabolic steroids can affect much more than skeletal muscle.
Another reason these results matter is that larger organs aren't automatically healthier organs. The researchers also found that the enhanced bodybuilders had higher resting heart rates and higher blood pressure than the natural athletes, suggesting their cardiovascular systems may already have been under greater stress. While this study didn't directly evaluate organ function, abnormal enlargement could be an early warning sign that these tissues aren't functioning optimally.
One question I know many people will ask is whether testosterone replacement therapy (TRT) carries the same risk. The honest answer is that we simply don't know yet.
TRT is steroid use—it's just administered at doses intended to restore normal physiological testosterone levels rather than produce the supraphysiological levels sought by many performance-enhancing drug users.
The study covered here wasn't designed to evaluate medically supervised TRT, so it's too early to draw conclusions one way or the other.
The bottom line is that anabolic steroids may be doing far more inside your body than simply helping you build bigger muscles. According to this new research, they also appear capable of enlarging vital organs such as the heart, liver, kidneys, and spleen.
Whether those changes ultimately lead to long-term health consequences remains to be seen, but it's another important reminder that the effects of anabolic steroids extend well beyond what you see in the mirror.
Fuchs, C. J., et al. When size goes inside: Visceromegaly in bodybuilders is not attributed to high protein intake but more likely associated with the use of appearance- and performance-enhancing drugs. Med Sci Sports Exerc, in press, 2026.
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