A groundbreaking study published in Medicine & Science in Sports & Exercise has definitively shown that the enlarged internal organs observed in bodybuilders result from PED use rather than high protein consumption. The research, led by Cas J. Fuchs and colleagues at Maastricht University, employed advanced MRI scanning to directly measure organ volumes in three distinct groups: recreational athletes, natural bodybuilders, and bodybuilders using appearance and performance-enhancing drugs (APED).
The study examined 45 men divided equally among the three groups. Natural bodybuilders consumed significantly more protein than controls, averaging 2.5 grams per kilogram (kg) of body mass daily compared to 1.4 grams per kg in recreational athletes. APED-using bodybuilders consumed even more at 2.9 grams per kg daily. Despite these elevated protein intakes being nearly double the amounts typically recommended for athletes, natural bodybuilders showed no increase in organ size compared to recreationally active controls.
The findings revealed dramatic differences in organ volumes among APED users. Heart volume measured 1.20 liters in APED users versus 0.89 liters in natural bodybuilders and 0.83 liters in controls. Liver volume showed similar patterns at 2.57 liters, 1.82 liters, and 1.79 liters respectively. Kidney volumes were more than 50 percent larger in APED users, while spleen volumes increased by approximately 35 to 40 percent.
Natural bodybuilders demonstrated substantial muscle development without corresponding organ enlargement. Their total lean body mass reached 160.3 pounds (72.7 kg) compared to 138.4 pounds (62.8 kg) in controls, reflecting pure muscle hypertrophy. APED users possessed even greater lean mass at 193.6 pounds (87.8 kg), but this increase reflected both enlarged muscles and significantly expanded internal organs.
The research team utilized whole-body MRI scanning to precisely quantify tissue volumes, a technique providing far more accurate measurements than previous estimation methods. APED users in the study reported an average of six years of PED use, with weekly testosterone dosages averaging 435 milligrams and total androgen dosages reaching 1,019 milligrams per week. Nearly all APED users (93.3 percent) used testosterone esters, while many combined multiple substances including growth hormone, insulin, and various anabolic steroids.
These findings directly contradict longstanding speculation within bodybuilding communities that very high protein intake causes organ enlargement. The visible abdominal distention sometimes observed in competitive bodybuilders, colloquially termed “bubble gut,” appears linked to internal organ expansion from drug use rather than dietary factors.
Natural bodybuilders maintained normal organ sizes despite protein intakes exceeding typical athletic consumption by 60 percent.
The health implications extend beyond cosmetic concerns. APED users in the study exhibited elevated resting heart rates and higher systolic blood pressure compared to both natural bodybuilders and controls, suggesting potential cardiovascular strain. While increased cardiac mass can represent normal adaptation to resistance training, the disproportionate enlargement observed raises concerns about long-term cardiovascular function and elevated risk of cardiac events.
The research provides quantitative evidence confirming what was previously based largely on anecdotal reports and isolated case studies. Lead researcher Fuchs stated that athletes need not worry about developing organ enlargement from high protein intake, though he noted limited benefit to consuming protein beyond 1.5 grams per kg daily for muscle development.
