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Can Skinny People Have Fatty Liver Disease?
What Lean Individuals Need to Know About Their Liver Risk
Nicholas Kruzdlo, B.S.
Physician Reviewed
Fatty Liver Disease, now clinically referred to as MASLD (Metabolic Dysfunction-Associated Steatotic Liver Disease), is most often linked to obesity and is commonly thought to affect only individuals with an elevated BMI. While obesity is one of the largest risk factors for developing MASLD, many other factors can lead to a "skinny individual" developing fatty liver disease. Patients characterized as having "lean MASLD" often have underlying issues related to visceral fat accumulation, genetics, metabolism, and demographic factors.
Studies estimate that 7-20% of fatty liver disease cases occur in patients with a normal BMI. This article will overview the risk profiles of these individuals and highlight how at risk you may be.
High Risk Group 1: Normal BMI with a High Visceral Fat ("Skinny Fat")
Fatty Liver Disease is defined as fat accumulation in the liver exceeding 5%. The fat that accumulates in organs differs from the fat stored beneath the skin. When most people think about body fat, they picture subcutaneous fat, which is visible to the naked eye. Subcutaneous fat often receives more attention than visceral fat. Visceral fat, however, accumulates around and within internal organs, including the liver, and is more harmful to overall health. While there is often a correlation between subcutaneous and visceral fat, some individuals may appear lean with minimal visible fat yet still have excess fat accumulation around their organs. This visceral fat promotes inflammation, insulin resistance, and fat storage within the liver, significantly increasing the risk of developing Fatty Liver Disease.
How do I Know if I Have Visceral Fat?
Today it is becoming increasingly easy to know how much visceral fat you may have. Technologies like the FibroScan, InBody, or DEXA scan are all non-invasive tests that can provide insight into body composition and liver health. Covenant uses these technologies to diagnose and monitor patients, helping ensure the highest chance of reversing Fatty Liver Disease.
High Risk Group 2: Lean Individuals With Genetic Predisposition and High Risk Demographics
Two individuals with similar lifestyles may have different risks of developing Fatty Liver Disease due to genetics. Genetics plays a significant role, especially in lean individuals. While not all genes involved in MASLD are known, several have been strongly associated with increased risk:
PNPLA3
TM6SF2
MOBAT7
Everyone carries these genes, but some individuals have variants (mutations) that impair the liver's ability to process and export fat, increasing disease risk regardless of body weight or BMI.
How Do I Know If I Have a Mutation?
Everyone has two copies of the genes above, one from each parent, giving us two total copies. If both copies function normally, there is no increased genetic risk. If one copy carries a mutation, risk is elevated. If both copies are mutated, the risk is significantly higher.
Genetic testing can identify these variants, but it may be costly, even as prices decrease. A more practical first step is to review your family history. If Fatty Liver Disease exists on both sides of your family, your risk may be increased, even if your BMI is normal.
These genetic mutations are also more common in certain ethnicities, including Asian, Pacific Islander, and Hispanic individuals. While Caucasians and African Americans have lower risks of lean Fatty Liver Disease, but it is still possible.
Group 3: Lean Individuals With Metabolic Dysfunction
Metabolic dysfunction can occur at any body size. Even lean individuals may experience insulin resistance, high cholesterol, or type 2 diabetes. A lean individual with type 2 diabetes and insulin resistance is at high risk for Fatty Liver Disease. One simple way to assess metabolic risk is through an HbA1c test, which measures average blood glucose levels over a three-month period.
HbA1c < 5.7: No increase in risk of Fatty Liver Disease
HbA1c 5.7-6.4: Elevation in risk of Fatty Liver Disease
HbA1c > 6.5: Biggest elevation in risk of Fatty Liver Disease
Mitigating Your Risk of Fatty Liver Disease
Leaner individuals with a normal BMI are often overlooked when it comes to screening for Fatty Liver Disease. If you identify with one of the groups above, you may be at an increased risk for "lean" or "skinny" Fatty Liver Disease, and screening is important. Additionally, adopting a protective lifestyle is key. This includes engaging regular exercise to build or maintain muscle mass, which helps combat visceral fat and insulin resistance and following a healthy dietary pattern. One of the most evidence-based approaches is the Mediterranean diet, which emphasizes lean proteins, healthy fats, vegetables, fruits, whole foods, and minimally processed carbohydrates. Combining a balanced diet with consistent exercise remains one of the most powerful tools for preventing and managing Fatty Liver Disease.
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