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PATHOLOGY PERSPECTIVES Consuming too many calories in general, and fat calories in particular, can overwhelm the liver's ability to metabolize fats normally. (Of course, it doesn't help that the average American gets roughly 40 percent of his or her calories from fat.) • It converts the ammonia left over from protein metabolism into urea that can be excreted. • It converts glucose to glycogen for storage; this can be released to help stabilize blood glucose levels. • It conserves iron from dead red blood cells for recycling. • It filters out toxins from the substances we ingest (food, alcohol, drugs, etc.). • It removes excessive hormones from the blood for excretion. • It stores several vitamins, including A, D, E, K, and B12. When liver function is impaired, any combination of these functions may be lost and many serious complications can arise. NONALCOHOLIC FATTY LIVER DISEASE Traditionally, we have associated liver disease with two main contributing factors: chronic wear and tear connected to drug or alcohol abuse, or long-term, low-grade inflammation related to viral infections. Now, with one-half of U.S. adults classified as overweight and one-fourth classified as clinically obese, another source of long-term liver stress is creating a new group of liver disease candidates— people with pathologic accumulation of triglycerides within their functioning liver cells, the hepatocytes. Consuming too many calories in general, and fat calories in particular, can overwhelm the liver's ability to metabolize fats normally. (Of course, it doesn't help that the average American gets roughly 40 percent of his or her calories from fat.) A person's body mass index (BMI) appears to have a direct correlation with his or her risk of having nonalcoholic fatty liver disease (NAFLD). In addition, insulin resistance—the condition of cells becoming less sensitive to the action of this important hormone—changes the way the 98 massage & bodywork march/april 2010 liver metabolizes nutrients. Insulin resistance is also tied closely to an elevated BMI. The overall consequence for the liver is that hepatocytes literally fill with triglycerides, and this interferes with the liver's ability to perform its vital functions. The label of NAFLD is applied specifically to people who develop fatter liver disease while consuming less than 10 grams of alcohol within a single week. This is equivalent to one 12-ounce beer, or one 4-ounce glass of wine, or one 1-ounce shot of liquor. It is fair to suggest that a lot of overweight people with liver problems consume more alcohol than this each week, but do not meet the criteria for excessive consumption that would put them at risk for alcoholic liver disease. Consequently, the number of people developing silent but potentially progressive liver disease may be even higher than reported under this classification system. PRIMARY LIVER DISEASE: THE NAFLD SPECTRUM • NAFLD: Nonalcoholic fatty liver disease is closely associated with high- fat diets and being overweight. It is estimated that up to 20 percent of all U.S. adults and 5 percent of all U.S. children would test positively for this condition, even without symptoms. It is usually a silent condition, and may not be recognized unless liver function tests are performed for some other reason. An overtaxed liver does secrete some enzymes called transaminases into the bloodstream, but the liver is so good at compensating for lost function that signs and symptoms tend to be minimal, subtle, and only very slowly progressive. For this reason, NAFLD by itself is sometimes described as a benign condition. • Some percentage of people with NAFLD progress to a more serious form of liver disease called nonalcoholic steatohepatitis, or