What is fatty liver disease?

Fatty Liver Disease: A Simple Explanation

Fatty liver disease occurs when excess fat builds up in your liver cells, affecting normal liver function and potentially leading to serious liver damage if left untreated. 1

What is Fatty Liver Disease?

• Fatty liver disease (specifically nonalcoholic fatty liver disease or NAFLD) is defined as the accumulation of fat in at least 5% of liver cells, visible through imaging or biopsy, without significant alcohol consumption or other secondary causes 1
• It represents a spectrum of liver conditions ranging from simple fat accumulation to more serious forms with inflammation and scarring 1
• NAFLD is the most common form of liver disease in the United States, affecting up to 30% of adults 2

Types of Fatty Liver Disease

NAFLD is divided into two main categories:

1. Nonalcoholic Fatty Liver (NAFL):

   • Simple fat accumulation in the liver (steatosis) without significant inflammation or liver cell damage 1
   • Generally has a slower progression and better prognosis 1

2. Nonalcoholic Steatohepatitis (NASH):

   • Fat accumulation with inflammation and liver cell injury (ballooning) 1
   • Can progress to fibrosis (scarring), cirrhosis, and even liver cancer 1, 2
   • Affects approximately 3-5% of the general population 1

Causes and Risk Factors

• Obesity: Present in approximately 50% of NAFLD cases 3
• Type 2 Diabetes: Present in about 20% of NAFLD cases and increases risk significantly 1, 3
• Metabolic Syndrome: Features like high blood pressure, high blood sugar, excess body fat around the waist, and abnormal cholesterol levels 1, 3
• Dyslipidemia: Abnormal blood fat levels present in approximately 70% of NAFLD cases 3
• Rapid Weight Loss: Especially in those who were initially obese 1
• Certain Medications: Some drugs can cause fat accumulation in the liver 1

How Fatty Liver Develops

• Excess calories, especially from carbohydrates and fats, are stored as triglycerides in liver cells 4
• Insulin resistance plays a key role, preventing normal fat metabolism 5
• Fat accumulation triggers oxidative stress and inflammation in some individuals, leading to NASH 4, 5
• This inflammatory process can activate liver stellate cells that produce scar tissue (fibrosis) 4

Symptoms and Progression

• Most people with fatty liver have no symptoms in early stages 2
• When symptoms do occur, they may include fatigue, discomfort in the upper right abdomen, and general malaise 1
• Simple fatty liver (NAFL) typically progresses slowly, if at all 1
• NASH can progress to cirrhosis over 5-10 years in some patients, especially those with diabetes or obesity 1
• People with NASH have higher risk of death from cardiovascular disease, cancer, and end-stage liver disease 2

Diagnosis

• Fatty liver is often discovered incidentally during tests done for other reasons 2
• Diagnosis requires:
  • Evidence of fat in the liver through imaging (ultrasound, CT, MRI) or biopsy 1
  • Exclusion of significant alcohol consumption and other causes of liver disease 1
• Blood tests may show elevated liver enzymes, but normal levels don't rule out fatty liver 1, 3
• Non-invasive tests like fibrosis scores or elastography can help identify those at risk of advanced disease 1, 2
• Liver biopsy remains the gold standard for diagnosing NASH and determining the stage of fibrosis 2

Treatment

• Weight loss through diet and exercise is the primary treatment for NAFLD 2, 5
  • Even modest weight loss (5-10% of body weight) can significantly improve liver fat and inflammation 5
• Mediterranean diet rich in fruits, vegetables, whole grains, and healthy fats is recommended 5
• Regular physical activity helps reduce liver fat even without significant weight loss 5
• Vitamin E may be beneficial for non-diabetic adults with biopsy-proven NASH 2, 5
• Medications targeting insulin resistance (like pioglitazone) or newer agents (GLP-1 agonists) show promise but are not yet standard treatment 5
• Bariatric surgery may be considered for those with obesity who don't respond to lifestyle changes 2

Common Pitfalls in Understanding Fatty Liver

• Assuming all fatty liver is caused by alcohol consumption 3
• Thinking normal liver enzymes rule out significant liver disease 3
• Believing fatty liver is always benign and doesn't require treatment 4
• Failing to recognize the connection between fatty liver and cardiovascular disease 1
• Not appreciating that even moderate alcohol consumption may worsen NAFLD in some individuals 6