Risks of Nonalcoholic Fatty Liver Disease

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Nonalcoholic fatty liver disease (NAFLD) is on the rise, along with skyrocketing rates of obesity and diabetes. What is nonalcoholic fatty liver disease — and how dangerous is a fatty liver to your longevity?

What Is Nonalcoholic Fatty Liver Disease?

Nonalcoholic fatty liver disease is the accumulation of fat in the liver that is not caused by overconsumption of alcohol. In most people, this common disease does not cause symptoms or complications, but in some people, the fat that accumulates can cause inflammation and scarring in the liver, which can lead to other issues.

Causes of Nonalcoholic Fatty Liver Disease

The disease was first named in 1980 after doctors had found a growing number of obese or diabetic patients had excess fat in their livers. The condition was mysterious because although patients insisted they were not drinking to excess, their livers had damage virtually identical to that found in alcoholics. Since then, researchers have discovered that while some fat in the liver is healthy and seems to pose no problem, once the amount of fat reaches 5 percent to 10 percent of the organ's total weight — the benchmark for fatty liver disease — it is much more vulnerable to damage like swelling, scarring and liver failure.

Though the exact cause of the disease is not known, there's evidence that eating too much food, or the wrong food (that is, highly-processed, high-fat food without proper nutrition), plays a major role.

How Nonalcoholic Fatty Liver Disease Affects Longevity

Researchers from Johns Hopkins University School of Medicine tackled this question in a 2011 study, published in the British Medical Journal.

Using data collected between 1994 and 1998 on 11,371 American men and women, the researchers determined which subjects had fatty livers. To their amazement, there appeared to be no excess risk of death after up to 18 years, among the adults with fatty liver disease. But they aren't sure why.

"We know that the liver is damaged by fatty liver disease as it progresses," says study author Mariana Lazo, an assistant professor of Medicine and Epidemiology at Johns Hopkins. "It may be that the body deposits fat in the liver as a kind of protective self-defense mechanism, to save the heart and other organs. But at a certain point, the liver fails, too. We may just not have discovered the point at which that happens."

In advanced liver disease, she says, fat disappears from the organ, so deaths ultimately due to fatty livers may be under-recorded, and more research is needed to find out the exact point at which nonalcoholic fatty liver disease may impact longevity.

In a similar finding, researchers from Queen's University in Kingston, Canada, examined the relationship between belly fat (either visceral or abdominal), and liver fat, with all-cause mortality. Their paper, published in 2006 in the journal Obesity, concluded that of the three risk factors, only visceral fat was associated with a greater risk of death.

The Takeaway

Even without evidence that excess mortality is associated with fatty liver disease, having too much fat in the liver puts it at risk of damage, and should be avoided.

"We have vaccines to prevent viral liver disease like hepatitis," says Lazo. "There's no vaccine against fatty liver disease and no drug to treat the damage caused by it. Prevention is key."

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Article Sources
  • Jennifer L. Kuk, Peter T. Katzmarzyk, Milton Z. Nichaman, Timothy S. Church, Steven N. Blair, and Robert Ross. "Visceral Fat Is an Independent Predictor of All-cause Mortality in Men." Obesity (2006) 14, 336–341; doi: 10.1038/oby.2006.43.
  • Lazo M, Hernaez R, Bonekamp S, Kamel IR, Brancati FL, Guallar E, Clark JM. “Non-alcoholic fatty liver disease and mortality among US adults: prospective cohort study.” BMJ. 2011 Nov 18;343:d6891.
  • Mayo Clinic. (2014, April 10). Nonalcoholic fatty liver disease. Retrieved February 24, 2016
  • Non-alcoholic Fatty Liver Disease (NAFLD). American Liver Foundation Public Information Sheet. Accessed December 19, 2012.