Fatty Liver Disease Causes and Diagnostic Approach

Primary Causes of Fatty Liver Disease

The American Association for the Study of Liver Diseases recommends considering metabolic dysfunction, with obesity, type 2 diabetes, and insulin resistance being the primary drivers of fatty liver disease, though secondary causes including medications, alcohol, and genetic conditions must be systematically excluded 1, 2
Obesity is the strongest risk factor for non-alcoholic fatty liver disease (NAFLD), present in the majority of cases, with prevalence reaching 30-40% in the general US population 1, 3
Type 2 diabetes mellitus is associated with a higher prevalence of NAFLD and more advanced disease, including non-alcoholic steatohepatitis (NASH) and fibrosis 2, 4
Dyslipidemia is part of the metabolic syndrome cluster that promotes hepatic steatosis 2

The American College of Gastroenterology notes that NAFLD prevalence increases with age, and older patients face a higher risk of progression to advanced fibrosis 1, 2
Men have approximately twice the prevalence of NAFLD compared to women 1, 2
Hispanic individuals have a significantly higher prevalence of NAFLD, while non-Hispanic blacks have a lower prevalence compared to non-Hispanic whites 1, 2
Genetic variants, such as PNPLA3 I148M, TM6SF2 E167K, and other variants, increase susceptibility to steatosis, inflammation, fibrosis, and hepatocellular carcinoma (HCC) risk 5

Excessive alcohol consumption, defined as >21 standard drinks/week in men or >14 drinks/week in women, is a secondary cause of fatty liver disease and must be excluded 4, 6
Hepatitis C (genotype 3) directly causes hepatic steatosis 1, 2, 7
Certain medications, such as amiodarone, methotrexate, tamoxifen, and corticosteroids, can cause fatty liver disease 1, 2, 7

The American Gastroenterological Association recommends using sensitive biomarkers, such as urine ethyl glucuronide and blood phosphatidylethanol, to assess alcohol history if under-reporting is suspected 5
A medication review should be performed to identify all steatogenic medications 5, 4
Competing liver diseases, such as hemochromatosis, autoimmune hepatitis, chronic viral hepatitis, alpha-1 antitrypsin deficiency, and Wilson's disease, must be excluded 4, 6
Metabolic risk factors, such as diabetes, lipid panel, BMI, and metabolic syndrome components, should be assessed 5, 8