Obesity Can Lead to Fatty Liver...a Silent Killer
Medical Author: Dennis Lee, MD
Medical Editor: Jay W. Marks, MD
Obesity is a major health problem worldwide. In the United States, roughly 300,000 deaths per year are related to obesity. Obesity also increases the risk of developing several chronic diseases such as type II diabetes, insulin resistance, coronary heart disease (responsible for heart attacks), cerebrovascular disease (responsible for strokes), high blood pressure, gout, gallstones, colon cancer, sleep apnea, and a form of liver disease called nonalcoholic fatty liver disease (NAFLD).
Obesity is defined as an excess amount of body fat. The normal amount of body fat (expressed as a percentage of body weight) is between 25-30% in women and 18-23% in men. Women with over 30% body fat and men with over 25% body fat are considered obese. Another easier way of defining obesity is by calculating the body mass index (BMI). The BMI is a mathematical formula that takes into account both a person's weight and height in calculating the degree of obesity. In adults, normal weight is defined as a BMI between 20 and 25 BMI units, overweight from 25 to 30, obesity from 30 to 35, significant obesity from 35 to 40, morbid obesity from 40 to 45, super obesity from 45 to 50, and super-morbid obesity greater than 50. Eighty percent of deaths related to obesity occurs in obese individuals with a BMI greater than 30. To find out what your BMI is, please refer to the Body Mass Index (BMI) Table for Adults, and the Body Mass Index (BMI) Index Table for Teens.
What is nonalcoholic fatty liver disease (NAFLD)?
Nonalcoholic fatty liver disease (NAFLD) refers to a wide spectrum of liver diseases ranging from the most common, fatty liver (accumulation of fat in the liver, also known as steatosis), to Nonalcoholic steatohepatitis (NASH, fat in the liver causing liver inflammation), to cirrhosis (irreversible, advanced scarring of the liver as a result of chronic inflammation of the liver). All of the stages of Nonalcoholic fatty liver disease are now believed to be due to insulin resistance, a condition closely associated with obesity. In fact, the BMI correlates with the degree of liver damage, that is, the greater the BMI the greater the liver damage.
The term Nonalcoholic is used because liver disease due to alcohol can show the same spectrum of liver disease as nonalcoholic fatty liver disease; however, patients with nonalcoholic fatty liver disease do not consume excessive amounts of alcohol.
Alarming statistics about nonalcoholic fatty liver disease
As expected, nonalcoholic fatty liver disease is observed principally in developed countries. In these societies, a sedentary lifestyle and high calorie, sugar, and fat intake lead to a high prevalence of obesity, insulin resistance, and diabetes.
Nonalcoholic fatty liver disease is currently the most common liver disease in the U.S. and worldwide, affecting estimated 10-24% of the world's population. In the U.S., the Centers for Disease Control reports that currently, approximately one half of the U.S. adult populationisoverweight (BMI>25) and one quarter of the U.S. adult population isobese(BMI>30). That means upwards of 29 million Americans have nonalcoholic fatty liver disease, while 6.4 million of these persons have nonalcoholic steatohepatitis (NASH). Even more alarming than these statistics, nonalcoholic fatty liver disease is occurring among children in the U.S.
In most patients nonalcoholic fatty liver disease causes no symptoms. Nonalcoholic fatty liver disease often is discovered when routine blood tests show slightly elevated levels of liver enzymes (ALT and AST) in the blood. Another way in which nonalcoholic fatty liver disease is discovered is when ultrasound examination of the abdomen is done for other purposes, say for looking for gallstones, and fat is found in the liver. In the late stages of non alcoholic fatty liver disease, the development of cirrhosis can lead to failure of the liver, swelling of the legs (edema), accumulation of fluid in the abdomen (ascites), bleeding from veins in the esophagus (varices), and mental confusion (hepatic encephalopathy). Patients with cirrhosis caused by Nonalcoholic fatty liver disease also may be at risk of developing liver cancer (hepatocellular carcinoma, HCC).