Anabolic-androgenic steroids increase organ size?

A “bubble gut” is often seen in high-level bodybuilders on stage, despite them having extremely low body fat levels. The reason for this is still unclear, but enlarged abdominal muscles, enlarged internal organs, and/or visceral fat between the organs may contribute.

It also remained unclear what is causing these bubble guts. It has been speculated that very high protein intakes and/or anabolic-androgenic steroids (AAS) play a role.

In our new study, we used MRI to assess organ volume in:

• Recreationally active males (control)
• Competitive male natural bodybuilders
• Competitive male bodybuilders using AAS (enhanced bodybuilders)

Key findings:

• The natural and enhanced bodybuilders had approximately double the protein intake when compared to the controls (2.5 and 2.9 vs 1.4 g/kg/d)
• Internal organ sizes were not greater in the natural bodybuilders compared to the control group, but the enhanced bodybuilders had substantially larger organs.

Interpretation?
Although the natural bodybuilders had much higher protein intake and greater lean mass when compared to the healthy controls, their organs were not larger. Because only the enhanced bodybuilders showed an increase in organ size, this suggests that AAS may be the primary contributor to the bubble gut.

Strengths and limitations
A strength of this study was the use of whole-body MRI to assess the actual size of several organs. A limitation is that it was a cross-sectional study, meaning that cause-and-effect cannot be proven.

Link to our study:
Fuchs 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 Exer, 2026

Go to the next infographic in the hormone series:
Testosterone injections increase organ size?