For people affected by NAFLD, the 10-year survival rate was about 80%. The rate of progression of fibrosis is estimated to be one per 7 years in NASH and one per 14 years in NAFLD, with an increasing speed. There is a strong relationship between these pathologies and metabolic illnesses (diabetes type II, metabolic syndrome). These pathologies can also affect non-obese people, who are then at a higher risk.Less than 10% of people with cirrhotic alcoholic FLD will develop hepatocellular carcinoma, the most common type of primary liver cancer in adults, but up to 45% people with NASH without cirrhosis can develop hepatocellular carcinoma.The condition is also associated with other diseases that influence fat metabolism. Causes
Fatty liver (FL) is commonly associated with metabolic syndrome (diabetes, hypertension, obesity, and dyslipidemia), but can also be due to any one of many causes:
Alcohol
Alcohol use disorder is one of the causes of fatty liver due to production of toxic metabolites like aldehydes during metabolism of alcohol in the liver. This phenomenon most commonly occurs with chronic alcohol use disorder. Metabolic
abetalipoproteinemia, glycogen storage diseases, Weber–Christian disease,  acute fatty liver of pregnancy, lipodystrophy
Nutritional
obesity, malnutrition, total parenteral nutrition, severe weight loss, refeeding syndrome, jejunoileal bypass, gastric bypass, jejunal diverticulosis with bacterial overgrowth
Drugs and toxins
amiodarone, methotrexate, diltiazem, expired tetracycline, highly active antiretroviral therapy, glucocorticoids, tamoxifen, environmental hepatotoxins (e.g., phosphorus, mushroom poisoning)
Other
celiac disease, inflammatory bowel disease, HIV, hepatitis C (especially genotype 3), and alpha 1-antitrypsin deficiency

Pathology
Fatty change represents the intracytoplasmatic accumulation of triglycerides (neutral fats).
At the beginning, the hepatocytes present small fat vacuoles (liposomes) around the nucleus (microvesicular fatty change). In this stage, liver cells are filled with multiple fat droplets that do not displace the centrally located nucleus. In the late stages, the size of the vacuoles increases, pushing the nucleus to the periphery of the cell, giving characteristic signet ring appearance (macrovesicular fatty change). These vesicles are well-delineated and optically "empty" because fats dissolve during tissue processing. Large vacuoles may coalesce and produce fatty cysts, which are irreversible lesions. Macrovesicular steatosis is the most common form and is typically associated with alcohol, diabetes, obesity, and corticosteroids. Acute fatty liver of pregnancy and Reyes syndrome are examples of severe liver disease caused by microvesicular fatty change. The diagnosis of steatosis is made when fat in the liver exceeds 5–10% by weight. Defects in fatty acid metabolism are responsible for pathogenesis of FLD, which may be due to imbalance in energy consumption and  its combustion,  resulting in lipid storage, or can be a consequence of peripheral resistance to insulin, whereby the transport of fatty acids from adipose tissue to the liver is increased. Impairment or inhibition of receptor molecules (PPAR-α, PPAR-γ and SREBP1) that control the enzymes responsible for the oxidation and synthesis of fatty acids appears to contribute to fat accumulation. In addition, alcohol use disorder is known to damage mitochondria and other cellular structures, further impairing cellular energy mechanism. On the other hand, non-alcoholic FLD may begin as excess of unmetabolised energy in liver cells.