NonAlcoholic Fatty Liver Disease (NAFLD)

What Is NAFLD?

Nonalcoholic fatty liver disease (NAFLD) is a spectrum of liver conditions characterized by the accumulation of excess fat (steatosis) in liver cells of people who drink little or no alcohol. When simple steatosis progresses to inflammation and liver cell injury, it is termed nonalcoholic steatohepatitis (NASH). NASH can lead to fibrosis, cirrhosis, and even liver cancer.

How Common Is It?

NAFLD is now the most common chronic liver disease worldwide. Estimates suggest that it affects about 25% of adults in North America and Europe and up to 30% in some Asian countries. Prevalence rises sharply in people with obesity, type2 diabetes, or metabolic syndrome, reaching 6080% in certain highrisk groups.

Main Causes and Risk Factors

Excess caloric intake, especially from saturated fats and refined carbohydrates.
Obesity, particularly central (visceral) obesity.
Insulin resistance and type2 diabetes.
High triglyceride levels and low HDLcholesterol.
Polycystic ovary syndrome (PCOS), hypothyroidism, and certain genetic variants (e.g., PNPLA3).
Sedentary lifestyle.
Certain medications (e.g., corticosteroids, amiodarone, some antiretrovirals).

How It Develops

The current multiplehit hypothesis suggests that NAFLD results from a combination of metabolic, inflammatory, and genetic factors:

Insulin resistance leads to increased free fatty acid flux into the liver.
The liver stores these fatty acids as triglycerides, causing steatosis.
Oxidative stress, mitochondrial dysfunction, and lipotoxicity trigger inflammation and cell death.
Proinflammatory cytokines and gutderived endotoxins perpetuate injury, promoting fibrogenesis.

Signs and Symptoms

Most people with early NAFLD are asymptomatic and discover the condition incidentally through abnormal liverfunction tests or imaging. When symptoms appear, they may include:

Fatigue or vague weakness.
Discomfort or a dull ache in the upper right abdomen.
Unexplained weight loss (more common in advanced disease).

Advanced fibrosis or cirrhosis can cause jaundice, swelling of the abdomen (ascites), spiderlike blood vessels, and easy bruising.

Diagnosing NAFLD

Diagnosis is a stepwise process:

History and physical exam to rule out significant alcohol intake and other liver diseases.
Blood tests liver enzymes (ALT, AST) are often mildly elevated, but normal levels do not exclude disease.
Imaging ultrasound is the firstline tool; FibroScan (transient elastography) and MRIPDFF provide quantitative assessments of fat and stiffness.
Noninvasive scoring systems e.g., NAFLD Fibrosis Score, FIB4, to estimate fibrosis risk.
Liver biopsy reserved for cases where the diagnosis is uncertain or when definitive staging is required. It remains the gold standard for distinguishing simple steatosis from NASH.

Stages of the Disease

Simple steatosis fat accumulation without inflammation.
Nonalcoholic steatohepatitis (NASH) steatosis plus inflammation and ballooning degeneration of hepatocytes.
Fibrosis scar tissue formation; graded from F0 (none) to F4 (cirrhosis).
Cirrhosis endstage scarring; risk of liver failure and hepatocellular carcinoma.

Treatment & Lifestyle Management

There is no approved medication specifically for NAFLD, so therapy focuses on addressing underlying metabolic abnormalities.

Weight Loss

Weight reduction of 710% of body weight can improve steatosis, reduce inflammation, and reverse fibrosis in many patients. Strategies include:

Caloriecontrolled diet (Mediterranean or DASH patterns are favoured).
Regular physical activity at least 150min/week of moderate aerobic exercise plus resistance training.

Control of Diabetes and Lipids

Optimizing glycemic control (e.g., metformin, GLP1 receptor agonists) and treating dyslipidaemia with statins are recommended. Some newer agents such as pioglitazone and the GLP1 analogue liraglutide have shown benefit in NASH trials.

Pharmacologic Options Under Investigation

Several drugs are in phaseIII trials, including obeticholic acid, resmetirom, and elafibranor. Until results are definitive, their use should be confined to clinical trials.

Alcohol and Hepatotoxins

Even lowlevel alcohol intake can exacerbate liver injury; most clinicians advise complete abstinence. Avoid unnecessary hepatotoxic medications.

Prevention Strategies

Maintain a healthy weight (BMI<25kg/m).
Adopt a balanced diet rich in fruits, vegetables, whole grains, lean protein, and healthy fats (olive oil, nuts).
Limit sugary beverages, processed foods, and excess saturated fat.
Engage in regular physical activity at least 30minutes most days.
Screen highrisk individuals (obesity, diabetes, metabolic syndrome) with liver enzymes or imaging.