Did you know that your liver may be storing too much fat even if you don’t drink alcohol? This condition, called nonalcoholic fatty liver disease NAFLD, is the most common liver disease in industrialized countries and affects around 25-35% of adults, 10% of people without obesity, and over 40% of children with obesity in the United States.
NAFLD is diagnosed when the liver contains more than 5-10% of its weight from fat. This is called steatosis and can impair the normal function of the liver and make it more vulnerable to damage. Over time, the fat accumulation triggers inflammation in the liver through the production of cytokines, which are chemical messengers that cause immune responses. This inflammation can damage the liver cells and cause non-alcoholic steatohepatitis (NASH), the more severe form of NAFLD. As the inflammation continues, scar tissue forms in the liver and replaces healthy tissue. This is called fibrosis, and it can lead to cirrhosis, which is the end stage of liver disease where most of the liver is scarred and cannot function properly.
You can think of the progression of NAFLD this way:
NAFLD → NASH → Fibrosis → Cirrhosis
NAFLD is also a risk factor for liver cancer. Even without cirrhosis, NAFLD can increase the risk of developing hepatocellular carcinoma (HCC), which is the most common type of liver cancer. Up to 45% of people with NASH can develop HCC.
NAFLD is caused by defects in fatty acid metabolism. This means that the body is not able to use or store fat properly. When we eat more carbohydrates than we need for energy, our body converts them into glucose (sugar). Some of this glucose is stored in the form of glycogen in our liver and muscles, but when these storage sites are full, the excess glucose is turned into triglycerides (fat) by the liver. This fat can build up in the liver cells and cause steatosis (fatty liver).
This process is worsened by insulin resistance, which is a condition where the cells do not respond well to insulin, a hormone that regulates blood glucose levels. Insulin resistance makes the body store more fat in the liver and also increases the release of fat from other tissues, such as fat cells, into the liver. Insulin resistance also affects the activity of certain molecules (PPAR-α, PPAR-γ, and SREBP1) that control the enzymes that break down or make fatty acids. When these molecules are impaired or inhibited, more fat accumulates in the liver.
NAFLD and NASH are often silent diseases that do not cause any symptoms until they’re advanced. So, it’s important to get screened for NAFLD if you have risk factors such as obesity, diabetes, high cholesterol, or high blood pressure. The earlier you detect NAFLD, the better you can prevent or treat it.
The most accurate way to diagnose NAFLD is by taking a small sample of liver tissue (biopsy) and examining it under a microscope. But this procedure is invasive and has some risks, so it is not always necessary. There are other ways to diagnose NAFLD without a biopsy.
One way is to look for risk factors that make NAFLD more likely, such as being overweight or obese, having insulin resistance, pre-diabetes or type 2 diabetes, having high triglycerides (a type of fat in the blood), or having elevated liver enzymes (a sign of liver damage). However, not all people with NAFLD have these risk factors, and not all people with these risk factors have NAFLD. Also, some people with NAFLD have normal liver enzymes, so they cannot be ruled out by a blood test alone.
Another way to diagnose NAFLD is by using imaging techniques that can show the amount of fat in the liver. These include ultrasound (US), computed tomography (CT), or magnetic resonance imaging (MRI). Among these, US is commonly used because it is affordable and does not expose the patient to radiation. US can also grade the severity of liver steatosis (fat) based on how bright the liver appears compared to other organs, such as the kidney. The brightness also affects how well the doctor can see the blood vessels, the liver tissue, and the diaphragm (the muscle that separates the chest from the abdomen) on the US image. The grading system for steatosis is as follows:
US is a reliable and reasonable method to diagnose NAFLD, with high sensitivity (ability to detect true cases) and specificity (ability to exclude false cases) compared to biopsy. However, CT imaging and MRI will yield an even greater level of accuracy. The best imaging modality may vary depending on the patient.
The great news is that NAFLD can be reversed if the underlying cause is reduced or removed. The main cause of NAFLD is excess carbohydrates in the diet, which are converted into glucose and then into triglycerides (fat) by the liver. When the liver cannot store or use all this fat, it accumulates in the liver cells and causes steatosis.
So, the best way to treat NAFLD is to reduce the intake of carbohydrates, especially from added sugars and high fructose corn syrup, and increase the intake of healthy fats. When we limit the consumption of sugars and starches, while increasing the intake of omega-3 fat sources, we see a metabolic shift take place. Now the body burns fat for energy instead of glucose and produces ketone bodies, which are fat-derived molecules that can be used by the brain and other organs.
A carbohydrate-restricted diet resulting in the production of ketone bodies not only helps to lose weight and reduce fat in the liver but also creates other benefits impacting NAFLD. Ketone bodies prevent de novo lipogenesis, which is the process of making new fat from glucose. It also increases fatty acid oxidation, which is the process of breaking down fat for energy. These processes prevent further accumulation of fat in the liver and help to clear out existing fat.
A carbohydrate-restricted lifestyle can heal NAFLD through various mechanisms:
Aside from consuming a carbohydrate-restricted diet, eating more fat from foods that contain omega-3 fatty acids can help to heal fatty liver disease and provide overall improvements in cardiometabolic health better than other forms of fat. Omega-3 fatty acids can reduce inflammation and improve liver function. Some examples of foods that contain omega-3 fatty acids are fish, shellfish, chia seeds, flax seeds, and walnuts.
One question that many people have is whether they need to follow a very low-carbohydrate, high-fat diet for the rest of their lives to prevent fatty liver disease from coming back. This is a reasonable question since changing one’s eating habits can be challenging and sometimes inconvenient. But the benefits of this diet are well worth it and can last for a long time.
Eating very low-carbohydrate, high-fat food can improve insulin sensitivity, which is a key factor for fatty liver disease. When the cells are more sensitive to insulin, they can use glucose (sugar) more efficiently and store less fat in the liver and other tissues. So, maintaining this diet for a long time can prevent or even reverse fatty liver disease. Of course, this diet doesn’t mean eating only meat and cheese. It means eating real, whole foods that are rich in nutrients and low in sugar and processed carbohydrates. It means eating plenty of vegetables, fruits, nuts, seeds, and healthy fats. It means eating enough protein from animal or plant sources. It means nourishing your body with life-giving foods that we can grow, hunt, or fish ourselves!