Palumboism, commonly called “HGH gut,” “bubble gut,” or “bodybuilder gut,” is an informal term for pronounced abdominal enlargement or distension seen in some highly muscular bodybuilders.
Despite its association with human growth hormone (HGH) in bodybuilding culture, Palumboism is not a formally recognized medical diagnosis, and scientists have not established HGH as its sole cause. Researchers have proposed several possible contributors, including growth hormone, insulin, anabolic-androgenic steroids, enlargement of internal organs, visceral tissue, abdominal muscle hypertrophy, diet, and the combined effects of appearance- and performance-enhancing drugs (APEDs).
HGH Gut
Scientific evidence specifically investigating the phenomenon remains limited. However, newer research is beginning to provide objective data about internal-organ enlargement in bodybuilders using APEDs.
What Is Palumboism?
“Palumboism” describes a disproportionately enlarged or protruding abdomen in an otherwise muscular and often lean physique. The appearance has attracted particular attention in competitive bodybuilding.
The term is widely used online and within bodybuilding communities but is not an established medical diagnosis with standardized diagnostic criteria. Researchers have proposed the term “abdominal hypertrophy syndrome” when discussing the phenomenon scientifically.
This distinction matters because abdominal enlargement can have many causes. A visibly distended abdomen in a bodybuilder does not by itself establish that the person has used HGH, insulin, anabolic steroids, or any other particular substance.
Why Is It Called Palumboism?
The term became associated with American bodybuilder Dave Palumbo and subsequently entered bodybuilding vocabulary as a description of pronounced abdominal distension in an extremely muscular physique.
Despite the name, Palumboism should not be treated as a formally defined disease named after an individual. Medical literature may instead describe relevant findings such as abdominal distension, visceral adiposity, abdominal muscle hypertrophy, or organ enlargement, depending on what is actually observed.
What May Cause Palumboism?
The exact cause of the abdominal appearance called Palumboism remains uncertain.
A 2024 review examining abdominal hypertrophy syndrome in bodybuilders discussed several potential contributors, including the use of growth hormone, insulin, anabolic-androgenic steroids, enlargement of visceral organs, visceral adiposity, connective-tissue changes, and hypertrophy of the abdominal musculature (Suslin et al., 2024).
Growth hormone is one proposed contributor because prolonged exposure to excessive growth hormone can affect tissues and internal organs. Insulin and anabolic steroids have also been suggested as possible contributors, particularly because bodybuilders may use multiple substances simultaneously.
However, biological plausibility is not the same as proof of causation.
Research specifically examining Palumboism is limited, and it is difficult to determine the contribution of any single substance when athletes may be using combinations of APEDs alongside intensive training and specialized diets.
For this reason, terms such as “HGH gut,” “insulin gut,” and “steroid gut” should not be interpreted as evidence that one particular drug has been proven to cause the appearance.
Is Palumboism the Same as Acromegaly?
No. Palumboism and acromegaly should not be considered the same condition.
Acromegaly is a recognized endocrine disorder caused by prolonged exposure to excessive growth hormone, most commonly because of a growth hormone-secreting pituitary tumor.
Persistently elevated growth hormone and insulin-like growth factor 1 (IGF-1) can cause changes throughout the body. These may include enlargement of the hands and feet, changes in facial features, joint problems, metabolic abnormalities, cardiovascular complications, and enlargement of some internal organs.
These established effects of chronic growth hormone excess provide a biological reason researchers have considered excessive HGH exposure as one possible contributor to abdominal enlargement in bodybuilders.
There is nevertheless an important difference. People described as having Palumboism may have been exposed to multiple performance-enhancing substances and other factors. Current evidence does not establish that their abdominal enlargement represents an artificially induced form of acromegaly.
Why Does the Abdomen Become Enlarged?
There may not be a single explanation for the characteristic abdominal appearance associated with Palumboism.
Researchers have proposed several possible mechanisms, including enlargement of internal organs, changes in visceral tissue, hypertrophy of the abdominal muscles, and effects associated with prolonged exposure to appearance- and performance-enhancing drugs.
The 2024 review of abdominal hypertrophy syndrome emphasized how limited the direct scientific evidence remains. Historically, many explanations for “HGH gut” have been based on observations within bodybuilding, known physiological effects of certain drugs, and proposed mechanisms rather than controlled studies specifically investigating Palumboism.
More recent research has provided objective evidence that enlargement of internal organs can occur in some bodybuilders using APEDs.
A 2026 study published in Medicine & Science in Sports & Exercise used magnetic resonance imaging (MRI) to compare 15 competitive male bodybuilders using APEDs, 15 competitive natural male bodybuilders, and 15 recreationally active men.
Researchers reported greater visceral-organ volumes in the APED-using bodybuilders than in both comparison groups. In contrast, visceral-organ volumes in natural bodybuilders were not significantly different from those of recreationally active controls (Fuchs et al., 2026).
The study provides evidence of an association between APED use and visceral-organ enlargement in the bodybuilders studied. It does not, however, establish that HGH was responsible for the differences.
That distinction is particularly important because APED users may take multiple substances. A study examining APED exposure as a group cannot determine how much of an observed difference is attributable specifically to growth hormone, insulin, anabolic steroids, another substance, or their combined effects.
Does HGH Cause “HGH Gut”?
There is currently insufficient evidence to say that HGH alone causes Palumboism.
Growth hormone remains biologically relevant to the discussion because prolonged GH excess is known to affect tissues and organs. Evidence of visceral-organ enlargement among APED-using bodybuilders also strengthens the rationale for investigating the potential effects of these substances.
But the available research does not justify turning that possibility into a simple cause-and-effect statement.
This is one reason the popular term “HGH gut” can be misleading. It embeds a causal explanation into the name even though the underlying phenomenon may involve multiple drugs, physiological changes, dietary factors, training practices, and individual differences.
Future studies that characterize participants’ drug exposure more precisely and follow bodybuilders over time may help researchers determine which factors contribute most strongly.
What Does the Research Actually Show?
Research specifically examining Palumboism remains sparse.
The 2024 review by Suslin and colleagues described abdominal hypertrophy syndrome as a poorly understood phenomenon and examined several proposed mechanisms. The review highlighted the lack of robust clinical evidence establishing why the characteristic abdominal appearance develops.
The 2026 study by Fuchs and colleagues provides stronger objective evidence for one proposed component: visceral-organ enlargement.
Using MRI rather than relying solely on visual observations, researchers found greater visceral-organ volumes among competitive male bodybuilders using APEDs compared with both natural bodybuilders and recreationally active controls.
That finding is important, but its limits are equally important.
The study included 45 men divided into three groups of 15, and it was not designed to establish whether HGH itself caused the differences. It therefore supports an association between APED use and visceral-organ enlargement in this population rather than proving that HGH causes Palumboism.
Taken together, current evidence supports continued investigation of organ enlargement and other physiological changes in APED-using bodybuilders while leaving the precise cause of Palumboism unresolved.
Is Palumboism Dangerous?
There is not enough evidence to classify Palumboism itself as a specific disease with a defined complication or mortality rate.
That does not mean the circumstances surrounding it are necessarily harmless.
Nonmedical use of growth hormone and other appearance- and performance-enhancing drugs can carry health risks independent of whether someone develops a distended abdomen. Growth hormone misuse in athletes has been associated with important health and safety concerns, particularly when supraphysiologic exposure or multiple performance-enhancing substances are involved (Holt, 2013).
Abdominal enlargement can also occur for reasons unrelated to bodybuilding or APED use. Persistent, unexplained, painful, or rapidly developing abdominal distension warrants medical evaluation rather than self-diagnosis based on appearance.
Can Palumboism Be Treated?
There are currently no established evidence-based treatment guidelines specifically for Palumboism.
Because Palumboism is not a standardized medical diagnosis and its underlying causes remain uncertain, there is no scientifically established treatment that can be recommended specifically to “reverse HGH gut.”
Someone who develops persistent or unexplained abdominal enlargement should seek medical evaluation to determine what is actually causing it. Depending on the individual, abdominal distension could involve gastrointestinal, metabolic, endocrine, structural, or other medical factors unrelated to bodybuilding.
People using non-prescribed growth hormone, insulin, anabolic steroids, or other performance-enhancing substances should tell their healthcare professional what they are taking. Accurate information about substance use may be important when evaluating possible metabolic, cardiovascular, endocrine, gastrointestinal, or other complications.
People who use insulin, growth hormone, or another medication for a diagnosed medical condition should not stop or change prescribed treatment without consulting the clinician managing their care.
Does Medically Prescribed Growth Hormone Cause Palumboism?
Current evidence does not establish Palumboism as an expected complication of appropriately prescribed growth hormone replacement therapy.
The phenomenon described as “HGH gut” has primarily been discussed in the context of bodybuilding and appearance- and performance-enhancing drug use, where doses, combinations of substances, and patterns of exposure may differ substantially from medically supervised treatment.
Growth hormone is a prescription medication with legitimate medical indications, including treatment of certain patients with documented growth hormone deficiency.
When medically indicated, treatment is prescribed and monitored according to the patient’s diagnosis and clinical circumstances.
The existence of “HGH gut” as a term in bodybuilding culture therefore should not be interpreted to mean that patients receiving medically indicated growth hormone therapy are expected to develop Palumboism.
Can Palumboism Be Prevented?
There is no scientifically validated protocol for preventing Palumboism because researchers have not established its precise cause.
Claims that particular HGH doses, drug combinations, diets, supplements, or training methods can prevent “HGH gut” are therefore not supported by sufficient clinical evidence.
The safest distinction is between medically indicated growth hormone treatment and nonmedical use of HGH or other performance-enhancing substances. Prescription growth hormone should be used only for an appropriate medical indication and under professional supervision.
When Should Abdominal Enlargement Be Evaluated?
A protruding abdomen should not automatically be labeled Palumboism simply because someone participates in bodybuilding.
Medical evaluation is particularly appropriate when abdominal enlargement is new, unexplained, progressive, painful, or accompanied by other symptoms.
A healthcare professional can assess whether the change may be related to gastrointestinal disease, an endocrine or metabolic disorder, medication or substance use, changes in body composition, or another cause.
People who use appearance- and performance-enhancing substances should disclose them during medical evaluation. Knowing which substances have been used, along with their duration and pattern of use, can provide important clinical context.
Final Thoughts
Palumboism, commonly called “HGH gut” or “bubble gut,” describes a recognizable abdominal appearance in bodybuilding, but its underlying causes remain incompletely understood.
Growth hormone, insulin, anabolic steroids, enlargement of internal organs, changes in visceral tissue, and abdominal muscle hypertrophy have all been proposed as possible contributors. However, current evidence does not establish HGH alone as the cause.
Research is beginning to provide stronger evidence for some proposed mechanisms. A 2026 MRI study found greater visceral-organ volumes in competitive male bodybuilders using appearance- and performance-enhancing drugs compared with natural bodybuilders and recreationally active controls. Because the study examined APED exposure rather than HGH in isolation, it cannot determine whether growth hormone itself produced those differences.
That distinction should remain central when discussing Palumboism. The popular term “HGH gut” implies a level of certainty that the scientific evidence does not currently support.
As research evolves, our understanding of abdominal enlargement in bodybuilders may change. For now, claims about exactly what causes, prevents, or reverses Palumboism should be treated cautiously, and persistent or unexplained abdominal enlargement should be medically evaluated rather than diagnosed based on appearance alone.
References
Fuchs, C. J., Brauwers, B., Trommelen, J., Yildiz, S., Widholm, P., Leinhard, O. D., Prompers, J. J., & van Loon, L. J. C. (2026). 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. Medicine & Science in Sports & Exercise, 58(9), 1878–1890. https://doi.org/10.1249/MSS.0000000000004011
Holt, R. I. G. (2013). Detecting growth hormone misuse in athletes. Indian Journal of Endocrinology and Metabolism, 17(Suppl. 1), S18–S22. https://doi.org/10.4103/2230-8210.119494
Suslin, I. A., Efimenko, I. V., Castrellon, R., & Husain, T. M. (2024). Abdominal hypertrophy syndrome: Characteristics and potential pathophysiology. Cureus, 16(10), e72026. https://doi.org/10.7759/cureus.72026