What Is Fatty Liver Disease?


By Franziska Spritzler

Fatty liver disease is becoming increasingly common in many parts of the world, affecting about 25 percent of people globally (1).

It is linked to obesity, type 2 diabetes and other disorders characterized by insulin resistance.

What’s more, if fatty liver isn’t addressed, it may progress to more serious liver disease and other health problems.

What Is Fatty Liver?

Fatty liver occurs when too much fat builds up in liver cells. Although it is normal to have a tiny amount of fat in these cells, the liver is considered fatty if more than 5 percent of it is fat (2).

While drinking too much alcohol can lead to fatty liver, in many cases it does not play a role.

A number of fatty liver conditions fall under the broad category of non-alcoholic liver disease (NAFLD), which is the most common liver disease in adults and children in Western countries (2, 3).

Non-alcoholic fatty liver (NAFL) is the initial, reversible stage of liver disease. Unfortunately, it often goes undiagnosed. Over time, NAFL may lead to a more serious liver condition known as non-alcoholic steatohepatitis or NASH.

NASH involves greater fat accumulation and inflammation that damages the liver cells. This can lead to fibrosis or scar tissue, as liver cells are repeatedly injured and die off.

Unfortunately, it is difficult to predict whether fatty liver will progress to NASH, which greatly increases the risk of cirrhosis (severe scarring that impairs liver function) and liver cancer (4, 5).

NAFLD is also linked to an increased risk of other diseases, including heart disease, diabetes and kidney disease (6, 7, 8).

Bottom Line: Fatty liver occurs when too much fat builds up in the liver. Fatty liver is reversible at an early stage, but it sometimes progresses to advanced liver disease.

What Causes Fatty Liver?

There are several factors that may cause or contribute to developing fatty liver:

  • Obesity: Obesity involves low-grade inflammation that may promote liver fat storage. It’s estimated that 30–90 percent of obese adults have NAFLD and it’s increasing in children due to the childhood obesity epidemic (2, 3, 9, 10).
  • Excess belly fat: Normal-weight people may develop fatty liver if they are “viscerally obese,” meaning they carry too much fat around the waist (11).
  • Insulin resistance: Insulin resistance and high insulin levels have been shown to increase liver fat storage in people with type 2 diabetes and metabolic syndrome (12, 13).
  • High intake of refined carbs: Frequent intake of refined carbs promotes liver fat storage, especially when high amounts are consumed by overweight or insulin-resistant individuals (14, 15).
  • Sugary beverage consumption: Sugar-sweetened beverages like soda and energy drinks are high in fructose, which has been shown to drive liver fat accumulation in children and adults (16, 17).
  • Impaired gut health: Recent research suggests that having an imbalance in gut bacteria, problems with gut barrier function (“leaky gut”) or other gut health issues may contribute to NAFLD development (18, 19).

Bottom Line: Causes of NAFLD include obesity, insulin resistance, excessive intake of refined carbs and sugar, as well as impaired gut health.

Symptoms of Fatty Liver

There are several signs and symptoms of fatty liver, although not all of these may be present. In fact, you may not even realize you have fatty liver.

  • Fatigue and weakness
  • Slight pain or fullness in the right or center abdominal area
  • Elevated levels of liver enzymes, including AST and ALT
  • Elevated insulin levels
  • Elevated triglyceride levels

If fatty liver progresses to NASH, the following symptoms may develop:

  • Loss of appetite
  • Nausea and vomiting
  • Moderate to severe abdominal pain
  • Yellowing of eyes and skin

It’s important to see your doctor regularly for standard exams and blood tests that can diagnose fatty liver at the early, reversible stage.

Bottom Line: Fatty liver may cause subtle symptoms and is often detected by blood tests. NASH usually involves more pronounced symptoms, such as abdominal pain and feeling unwell.

Dietary Strategies for Getting Rid of Fatty Liver

There are several things you can do to get rid of fatty liver, including losing weight and cutting back on carbs. What’s more, certain foods can help you lose liver fat.

Lose Weight and Avoid Overeating If Overweight or Obese

Weight loss is one of the best ways to reverse fatty liver if you are overweight or obese.

In fact, weight loss has been shown to promote loss of liver fat in adults with NAFLD, regardless of whether the weight loss was achieved by making dietary changes alone or in combination with weight loss surgery or exercise (20, 21, 22, 23, 24).

In a three-month study of overweight adults, reducing calorie intake by 500 calories per day led to an 8 percent loss of body weight, on average and a significant decrease in fatty liver score (21).

What’s more, it appears that the improvements in liver fat and insulin sensitivity may persist even if some of the weight is regained (25).

Cut Back on Carbs, Especially Refined Carbs

It may seem as though the most logical way to address fatty liver would be to cut back on dietary fat.

However, researchers report only about 16 percent of liver fat in people with NAFLD comes from dietary fat. Rather, most liver fat comes from fatty acids in their blood and about 26 percent of liver fat is formed in a process called de novo lipogenesis (DNL) (26).

During DNL, excess carbs are converted into fat. The rate at which DNL occurs increases with high intakes of fructose-rich foods and beverages (27).

In one study, obese adults who consumed a diet high in calories and refined carbs for three weeks experienced a 27 percent increase in liver fat, on average, even though their weight only increased by 2 percent (15).

Studies have shown that consuming diets low in refined carbs may help reverse NAFLD. These include low-carb, Mediterranean and low-glycemic index diets (28, 29, 30, 31, 32, 33, 34).

In one study, liver fat and insulin resistance decreased significantly more when people consumed a Mediterranean diet than when they consumed a low-fat, high-carb diet, even though weight loss was similar on both diets (33).

Although both Mediterranean and very low-carb diets have been shown to reduce liver fat on their own, one study that combined them showed very impressive results.

In this study, 14 obese men with NAFLD followed a Mediterranean ketogenic diet. After 12 weeks, 13 of the men experienced reductions in liver fat, including three who achieved complete resolution of fatty liver (31).

Include Foods That Promote Loss of Liver Fat

In addition to cutting back on carbs and avoiding excess calorie intake, there are certain foods and beverages that may be beneficial for fatty liver:

  • Monounsaturated fats: Research suggests that eating foods high in monounsaturated fatty acids like olive oil, avocados and nuts may promote liver fat loss (35, 36).
  • Whey protein: Whey protein has been shown to reduce liver fat by up to 20 percent in obese women. In addition, it may help lower liver enzyme levels and provide other benefits in people with more advanced liver disease (37, 38).
  • Green tea: One study found that antioxidants in green tea called catechins helped decrease liver fat and inflammation in people with NAFLD (39).
  • Soluble fiber: Some research suggests that consuming 10–14 grams of soluble fiber daily may help reduce liver fat, decrease liver enzyme levels and increase insulin sensitivity (40, 41).

Bottom Line: Losing weight, avoiding overeating, including certain foods in your diet and cutting back on sugar and carbs may help reduce liver fat.

Exercise That Can Help Reduce Liver Fat

Physical activity can be an effective way to decrease liver fat.

Studies have shown that engaging in endurance exercise or resistance training several times a week can significantly reduce the amount of fat stored in liver cells, regardless of whether weight loss occurs (42, 43, 44).

In a four-week study, 18 obese adults with NAFLD who exercised for 30–60 minutes five days per week experienced a 10 percent decrease in liver fat, even though their body weight remained stable (44).

High-intensity interval training (HIIT) has also been shown to be beneficial for decreasing liver fat (45, 46).

In a study of 28 people with type 2 diabetes, performing HIIT for 12 weeks led to an impressive 39 percent reduction in liver fat (46).

However, even lower-intensity exercise can be effective at targeting liver fat. According to a large Italian study, it appears that how much you exercise is most important.

In that study, 22 diabetics who worked out twice per week for 12 months had similar reductions in liver fat and abdominal fat, regardless of whether their exercise intensity was considered low-to-moderate or moderate-to-high (47).

Since working out regularly is important for reducing liver fat, choosing something you like doing and can stick with is your best strategy.

Bottom Line: Endurance exercise, strength training or high- or low-intensity interval training can help reduce liver fat. Working out consistently is key.

Supplements That May Improve Fatty Liver

Results from several studies suggest that certain vitamins, herbs and other supplements may help reduce liver fat and decrease the risk of liver disease progression.

However, in most cases, experts say that further research is required to confirm this.

In addition, it’s important to speak with your doctor before taking any supplements, especially if you are taking medication.

Milk Thistle

Milk thistle, or silymarin, is an herb known for its liver-protecting effects (48).

Some studies have found that milk thistle, alone or in combination with vitamin E, may help reduce insulin resistance, inflammation and liver damage in people with NAFLD (49, 50, 51, 52).

In a 90-day study of people with fatty liver, the group who took a silymarin-vitamin E supplement and followed a low-calorie diet experienced twice the reduction in liver size as the group who followed the diet without taking the supplement (52).

The dosages of milk thistle extract used in these studies were 250–376 mg per day.

However, although experts believe that milk thistle shows promise for use in NAFLD, they feel that more studies are needed to confirm its effectiveness for both short- and long-term use (53).


Berberine is a plant compound that has been shown to significantly reduce blood sugar, insulin and cholesterol levels, along with other health markers (54).

Several studies also suggest that it may benefit people with fatty liver (55, 56, 57).

In a 16-week study, 184 people with NAFLD reduced their calorie intake and exercised for at least 150 minutes per week. One group took berberine, one took an insulin-sensitizing drug and the other group took no supplement or medication (57).

Those taking 500 mg of berberine, three times per day at meals, experienced a 52 percent reduction in liver fat and greater improvements in insulin sensitivity and other health markers than the other groups.

Researchers say that despite these encouraging results, further studies are needed to confirm berberine’s effectiveness for NAFLD (58).

Omega-3 Fatty Acids

Omega-3 fatty acids have been credited with many health benefits. The long-chain omega-3s EPA and DHA are found in fatty fish, such as salmon, sardines, herring and mackerel.

Several studies have shown that taking omega-3s may improve liver health in adults and children with fatty liver (59, 60, 61, 62, 63).

In a controlled study of 51 overweight children with NAFLD, the group who took DHA had a 53 percent reduction in liver fat, compared to 22 percent in the placebo group. The DHA group also lost more belly fat and fat around the heart (60).

Furthermore, in a study of 40 adults with fatty liver, 50 percent of those who took fish oil in addition to making dietary changes had reductions in liver fat, while 33 percent experienced a complete resolution of fatty liver (63).

The dosages of omega-3 fatty acids used in these studies were 500–1,000 mg per day in children and 2–4 grams per day in adults.

Although all the studies above used fish oil, you can get the same benefits by consuming fish high in omega-3 fats several times a week.

Importantly, these studies show that certain supplements appear to enhance the effects of lifestyle changes. Taking them without following a healthy diet and exercising regularly will likely have little effect on liver fat.

Bottom Line: Supplements that may help reverse NAFLD include milk thistle, berberine and omega-3 fatty acids. They are most effective when combined with lifestyle changes.

Take Home Message

Fatty liver can lead to a number of health problems. Fortunately, it can be reversed if addressed at an early stage.

Following a healthy diet, increasing physical activity and perhaps taking supplements can reduce excess liver fat and decrease the risk of its progression to more serious liver disease.

Reposted with permission from our media associate Authority Nutrition.

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