You may never have heard of nonalcoholic fatty liver disease or NAFLD—but you might have this serious disease and be completely unaware until it’s advanced.

NAFLD is becoming more and more common, and it is one of the leading causes of more severe liver diseases. Stunning statistic: Research shows that 30% of adults and close to 10% of children in the US have NAFLD, with more at risk.

Having a fatty liver used to be linked almost exclusively with long-term and heavy drinking. The newer “nonalcoholic” type of the disease was so named when the health community realized that more and more, fatty liver was developing in people without a drinking problem.

The condition starts as NAFL–without the D. This means that you have too much fat in your liver but little to no inflammation or damage to cells. But as time passes and inflammation increases, so does damage to the liver.

Unchecked, NAFL can progress to NASH, or nonalcoholic steatohepatitis. This means there is severe inflammation in your liver that can lead to the formation of scar tissue throughout the liver. NASH is one of the most common causes of cirrhosis, when scar tissue is so widespread that it affects liver function. It can also lead to liver failure or liver cancer. Estimates vary, but according to the NIH (National Institutes of Health), between 3% and 12% of adults have NASH…and over 20% of them are at risk for developing cirrhosis.

Fatty liver does not have any unique or distinct symptoms. You may experience fatigue or achy or sharp pain in the upper right side of your abdomen, but these are hard to distinguish from symptoms of many other conditions. You may also have no symptoms at all.

This helps to explain why fatty liver disease is usually found by accident—when people have tests for other reasons.

The results of blood tests that measure liver enzymes (among other chemicals) are one way to detect damage caused by excess fat in the liver. Be sure to ask your doctor to order this “comprehensive metabolic panel” when you’re having other blood tests and, of course, be sure to get your yearly wellness exam—putting it off allows fatty liver disease to progress.

CT scans, ultrasounds and MRI scans of the abdomen can pinpoint a fatty liver. If your doctor suspects NAFLD, you may have a test called vibration-controlled transient elastography to look for increased stiffness in the organ, a sign of scar tissue. A biopsy might be ordered to see if you have NASH.

SOMETHING YOU EAT IS THE PROBLEM

NAFLD is associated with obesity, type 2 diabetes, high blood pressure, high cholesterol and polycystic ovary syndrome (PCOS). Brent Tetri, MD, professor of internal medicine at Saint Louis University School of Medicine and an expert on NAFLD, explains that all of these include the same underlying condition—insulin resistance, or insulin not working well in the body. And that condition, in turn, can often be traced back to a big problem in many people’s diets—an overload of sugar.

What’s going wrong: Sugars are a type of carbohydrate (fiber and starches are the other two). One of the liver’s many functions is to turn the carbs you eat into fat, which is then stored in fat tissue for future fuel needs. This is normal metabolism in action. But keep in mind that the liver doesn’t treat all types of carbs or all types of sugars the same way. For instance, the liver processes glucose (normal blood sugar) and fructose differently. The liver can store glucose or not take it up at all, but all of the fructose in the bloodstream goes straight to the liver and is turned into fat. If there’s more fat created from the fructose than the liver can process, the organ becomes overwhelmed and the fat doesn’t get moved out to storage—it hangs around, clogging the liver.

A key culprit is table sugar, or sucrose—it’s actually half fructose. Dr. Tetri cautions that everyday table sugar is just as bad for you as the high-fructose corn syrup that many people already avoid. Processed foods made with a variety of added sugars add to the fructose overload.

WHAT CAN YOU DO?

The good news is that by changing the way you eat, you can head off or even reverse NAFLD. Dr. Tetri says smart diet changes can have a big effect on the liver. The same type of diet that’s good for your heart and brain is good for your liver, so be sure to get lots of vegetables, fruit in moderation (yes, fruit has fructose, but it’s balanced by fiber and other nutrients), some olive oil, fish and whole grains. (If you think that sounds like the essence of the Mediterranean diet, you’re correct.)

What to avoid is equally important. Besides high-fructose corn syrup and sugar, skip trans fats altogether (read labels carefully—they’re still in some foods, notably those with partially hydrogenated vegetable oils), and be smart about which foods with saturated fat you eat because certain foods high in saturated fat—notably fatty meat and dairy foods—can increase the risk for heart disease and stroke and have been associated with NASH in animal studies. Healthful foods that contain saturated fat include fatty fish, nuts and seeds. And having an alcoholic drink does not appear to add to the damage in NASH, so if you want to have a glass of wine with your salmon, that’s okay (but certainly excessive alcohol should be avoided).

Studies have shown that obese people who lose 5% of their body weight will reduce fat in their livers, and most people who lose 10% of their body weight can make NASH go away completely. Also, exercise even without weight loss increases liver health.

There is also a supplement that may offer some benefits, Dr. Tetri says—milk thistle. There’s no trial data, but this supplement isn’t likely to hurt the liver and it might help. Also, people who drink two to three cups of coffee a day have a lower risk of liver disease, and it doesn’t matter whether it’s regular or decaffeinated coffee.

What’s dangerous: Acetaminophen (Tylenol) taken at doses that exceed 2,000 mg a day (talk to your doctor about the correct amount for you)…black cohosh, often taken to ease menopause symptoms… and kava kava, used for stress reduction and weight loss. These can all damage your liver.

There are encouraging developments in medications for NASH. Five clinical trials are in the last phase of testing before going to the FDA for potential approval. Future treatment will likely include combination drugs aimed at different mechanisms in the disease pathway, much like high blood pressure and diabetes are treated now.