The liver is essential for digestion, metabolism, detoxification, and fluid regulation. While alcohol abuse is a known cause of liver disease, affecting 4.7% of U.S. adults, non-alcoholic fatty liver disease (NAFLD), strongly associated with diet, is far more common, impacting 24% of adults and up to 70% of those with diabetes. Polycystic ovarian syndrome (PCOS), hypothyroidism, obstructive sleep apnea, and other conditions can also increase risk.

Progression of Fatty Liver Diseases

Fatty liver disease progresses through five stages: steatosis, steatohepatitis, fibrosis, cirrhosis, and liver failure.

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Steatosis

In the first stage, steatosis, the liver simply accumulates excess fat, but functions effectively without inflammation.

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Steatohepatitis

However, steatosis can progress to nonalcoholic steatohepatitis (NASH) in which case the liver is inflamed and compromised as in alcoholic related steatohepatitis (ASH). Symptoms can include pain in the upper right quadrant of the abdomen, weakness/fatigue, itching, and even jaundice, a yellowing of the skin and eyes.

Liver Fibrosis

Liver fibrosis occurs when scarring replaces healthy liver tissues and occurs in surrounding vessels. Continued hepatic assaults, including dietary, alcoholic, viral, and medicinal, can facilitate the transition of steatohepatitis to liver fibrosis.

Liver fibrosis has five categories: minimal, mild, moderate, to severe chronic levels of hepatitis.

Symptoms in the latter categories include difficulty thinking clearly, nausea, and fluid buildup in the abdominal area and legs.

Apart from consumption causes, hepatitis B (HBV) and hepatitis C (HCV) viruses can cause liver fibrosis without the preceding fatty liver stages. Medications such as non-steroidal anti-inflammatory drugs, anabolic steroids, birth control pills, and other drugs can also be the direct cause.

Cirrhosis

Cirrhosis is the most severe stage in which case the liver is permanently damaged. Dietary and lifestyle treatments can slow the progression but cirrhosis can progress to liver failure and even into liver cancer.

Predisposition and Lifestyle

The development of NAFLD is multifactorial, involving a genetic predisposition, insulin resistance, and metabolic syndrome components such as obesity, dyslipidemia, and hypertension. The presence of T2DM not only increases susceptibility but also accelerates the progression to more severe forms such as NASH, fibrosis, and cirrhosis.

High intake of saturated fats, often in red meat, and simple, refined carbohydrates, which are often high in ultra-processed foods and refined grains, contribute significantly to insulin resistance and the development of steatosis and the progression to steatohepatitis. Weight loss of even only 7-10% from regular physical activity and diet is associated with steatohepatitis reversal.

Detection and Diagnosis

Blood tests showing elevated liver enzymes, such as alanine aminotransferase (ALT) and aspartate aminotransferase (AST) can be the first indicators of a compromised liver. Imaging techniques, including ultrasound, computed tomography (CT), and magnetic resonance (MRI), can help confirm with a liver biopsy being used when these less invasive tests are inconclusive.

Summary and Conclusion

Non-alcoholic fatty liver disease (NAFLD) generally progresses through five main stages: steatosis, steatohepatitis, liver fibrosis, cirrhosis, and liver failure. Although viruses and medications can directly cause liver fibrosis/scarring, diet is the most common cause being at the crux of obesity, type 2 diabetes, insulin resistance, and dyslipidemia and playing a strong role in PCOS and hypothyroidism. Reducing or eliminating refined, processed carbohydrates and foods high in saturated fat can reverse this sometimes-fatal condition

Registered dietitians, particularly familiar with NAFLD can be an indispensable and perhaps primary part of a medical team in preventing, managing, and reversing this potentially fatal and debilitating, highly prevalent chronic disease.