Micrograph of non-alcoholic fatty liver disease. The liver has a prominent (centrilobular) macrovesicular steatosis (white/clear round/oval spaces) and mild fibrosis (green). The hepatocytes stain red. Macrovesicular steatosis is lipid accumulation that is so large it distorts the cell's nucleus. (Credit: Nephron/Wikimedia Commons)

Today, up to 25 percent of people in the U.S. are living with non-alcoholic fatty liver disease (NAFLD), according to the American Liver Foundation. NAFLD is a medical condition associated with obesity that can eventually lead to other liver conditions or even liver failure. In less than a decade, NAFLD will likely become the number one cause of liver transplants in the country, and demand will continue to overwhelm the supply of livers available.

NAFLD presents a major health risk because it is linked to several of our society’s toughest health issues. The disease, which describes the accumulation of excess fat in the liver, closely correlates with the obesity epidemic. Yet NAFLD has also become intertwined with our country’s fixation on alcohol consumption and binge drinking because both put great stress on our livers. For Americans with NAFLD, drinking too much can pose an especially serious risk of liver damage.

As a hepatologist, it’s difficult not to see non-alcoholic fatty liver disease as one of the most pressing healthcare issues in the country. Today, about one third of Americans are obese, with rates expected to top 60 percent in thirteen U.S. states by 2030, according to a recent report issued jointly by the Trust for America's Health and the Robert Wood Johnson Foundation. A genetic predisposition to obesity or diabetes, lack of exercise and poor diet—all of which remain major health issues in the U.S.—are all contributing factors to NAFLD. Rates of the disease are expected to continue to rise and will pose a major health risk to many Americans in coming years.

Physical activity can help prevent NAFLD. (Ed Yourdon/Flickr)

But the disease is far from unbeatable. NAFLD is well worth taking a closer look at because it is both preventable and reversible in most cases.

NAFLD describes the accumulation of fat in hepatocytes, or liver cells, in excessive amounts. These fats are typically triglycerides, which the body naturally stores and creates from calories that it doesn’t need right away. Normally these fats are burned off for energy, but if the body is overwhelmed with calories and a lack of exercise, then the triglycerides are simply never released. They instead accumulate in the liver and cause NAFLD, which can lead to inflammation, scarring, liver dysfunction and even liver cancer.

Exercise and nutritional improvements can reverse and fend off NAFLD, yet many people fail to apply these lifestyle prescriptions for a number of reasons. And NAFLD presents its own special set of challenges. Of most concern is the fact that NAFLD is largely asymptomatic before it begins causing problems. Obesity inflicts a number of noticeable concerns like joint pain, heart palpitations and high blood pressure. But the liver is extremely robust and may struggle with NAFLD for five to ten years before the organ raises its own red flag.

The liver’s fortitude is what helps it perform a diverse range of functions that protect us from toxins we consume, like excess amounts of calories, alcohol and prescription drugs. Yet its incredible resilience suggests to many individuals that these toxins present little or no risk to their bodies.

Excessive alcohol consumption can damage the liver. (GW Fins/Flickr)

That means many people place enormous amounts of pressure on their liver without considering the risk of a metabolic shutdown. Alcohol consumption is a great example. When alcohol is metabolized, it produces a toxic enzyme called acetaldehyde in the liver. After years of processing heavy amounts of the toxin, liver cells can become permanently inflamed or scarred. But even though there is broad awareness that alcohol causes liver damage, few people consider alcohol consumption to be a true health risk. For someone who also has NAFLD, the intense stress already placed on the liver by alcohol can become more dangerous or create additional liver problems earlier in life.

Pain relievers are another example of the everyday stress we place on our livers. Millions of Americans use acetaminophen, the active ingredient in Tylenol, every year. Ironically, drugs like Tylenol that are often used by obese individuals to ease their short-term joint pain are contributing to long-term liver damage. In excess amounts, acetaminophen builds up in the liver and obstructs the pathways it uses to dispel toxins, and as with alcohol, the risks can be compounded for someone who also has NAFLD. Even some vitamins, nutritional supplements and other herbal medications that are used to improve overall health and diet contain ingredients or chemicals that can cause strain on the liver.

NAFLD is closely linked to obesity. (Jennifer Yin/Flickr)

Certain groups of people may also have an increased risk of NAFLD. Hispanics, for instance, are at least two times as likely than Caucasians to carry a gene called PNPLA3, which drives the liver to produce excess triglycerides.

NAFLD is placing an extraordinary amount of strain on millions of livers each year, and when excessive alcohol consumption and the overuse of certain drugs are added to the mix, those risks become even greater. Taken together, rising NAFLD rates represent a looming large-scale health challenge in America. Today, nearly 16,000 people are on the waiting list for a liver transplant, but only about 6,000 transplants are performed each year.

For the most part, however, the increased stress we are placing on livers is preventable. Fatty liver disease is the most commonly diagnosed liver problem in the U.S., and we can better address it by understanding the direct and indirect causes that put people at risk, and by making sure our healthcare system is prepared to address a liver transplant demand that is likely to rise drastically in the coming decade.