Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

Nonalcoholic fatty liver disease is now the most frequent chronic liver disease, thanks, in part, to our epidemic of obesity––now even seen in children. As many as nearly 70 to 80 percent of obese children may have fatty liver disease. Why do we care? Because a fatty liver can progress into fatty hepatitis, which can cause scarring and liver cirrhosis––which is bad enough without also causing you to develop liver cancer, too.

Okay, so what’s the source of the liver fat in fatty liver disease? There are three main sources: the excess sugar in our diet, excess fat in our diet, and the fat spilling over from your own excess body fat.

How do we know excess dietary sugar is bad? Because it’s been put to the test. If you randomize teens with fatty liver disease to a diet low in free sugars (meaning added sugar and sugary beverages), they experience a significant improvement within eight weeks. Given this new data, a liver journal editorial read, “[a] strong argument can be made that we are beyond any period of uncertainty about the harmful effects of excess sugar consumption and that we must now act … to inform the public of the health risks of eating too much sugar.”

How do we know excess dietary fat is bad? Because it’s been put to the test. Randomize people to the same low-calorie diet, but one that’s low-fat versus one that’s high-fat, and within just two weeks, the low-fat diet decreased liver fat by 20 percent, whereas the same number of calories on a high-fat diet increased liver fat by 35 percent!

On the low-fat diet, insulin levels went down about 15 percent, and on the high-fat diet, insulin went up about 15 percent. Low-carb and ketogenic diet advocates are always talking about how you have to eat more fat and less carbs to keep your insulin levels down, but the exact opposite happens when it’s actually put to the test. Even a single high-fat meal not only increases liver fat, but also insulin resistance. Within four hours, your whole-body insulin sensitivity can drop by 25 percent; so, your body has to pump out that much more insulin. As the accompanying editorial put it, a single fat dose packs a punch.

So, to help prevent or treat fatty liver disease, patients should limit or avoid eating fat-rich foods. While more long-term clinical trials are always needed, based on current evidence, we would recommend a diet low in fat, notably saturated fat––so, low in meat, dairy, and junk, and low in refined carbs, notably soda.

Saturated fat is not only more metabolically harmful for the human liver than unsaturated fat; saturated fat is more harmful than straight sugar. If you overfeed people with 1,000 calories of saturated fat (like cheese and coconut oil), unsaturated fat (like nuts and olive oil), or sugar (like soda and candy), overeating 1,000 calories a day of anything isn’t good for you, but the saturated fat increased liver fat 55 percent, significantly more than the unsaturated fats, with the candy coming in between.

So, in terms of weight loss, although beneficial, certain diets can actually cause or exacerbate this disease––such as very low-carbohydrate, high-fat diets––whereas those eating healthy plant-based diets may lower the risk of fatty liver disease. For example, the consumption of legumes (beans, split peas, chickpeas, and lentils) is associated with a lower risk of fatty liver––up to 65 percent lower odds eating more beans.

Now, in this study, they weren’t looking at people eating strictly plant-based diets, just more or less so. It’s harder to study those eating completely meat-free diets, since they currently represent just a small segment of the U.S. population. But what about Americans of Indian descent? Those originating from the Indian subcontinent are one of the fastest growing ethnic groups in the United States, and they appear to largely retain their diets, with about the same percentage of vegetarians as in India—nearly 40 percent. We know in India itself nonvegetarians (those who eat meat) are at significantly higher risk of fatty liver disease. In Taiwan, you see the same thing: vegetarians at significantly lower risk. And even the vegetarians who were affected had significantly less liver scarring. Their data suggests that replacing a single serving of soy with a serving of meat or fish was associated with 12 percent to 13 percent increased risk of fatty liver disease. But what about here in the United States?

Eating vegetarian was associated with being slimmer, having better blood sugars, better cholesterol, and less than half the odds of fatty liver disease. You don’t know if it’s cause-and-effect, though, until you put it to the test. In an effort to reverse a fatty liver patient’s inflammatory bowel disease with a plant-based diet, liver inflammation was dramatically improved. But, he also lost about 9 pounds in the first 11 days thanks to eating healthy; so, it’s hard to tease out the specific diet effects. In fact, you have to be careful about rapid weight loss, because all that extra fat being broken down can flood into the bloodstream and sometimes make things worse. So, for fatty liver disease patients, losing like three pounds a week might be safer.

Even though plant-based diets have yet to be properly put to the test in a randomized clinical trial for fatty liver disease, I would submit that they are still the best diet for fatty liver disease. Not based on a single case report, but based on the fact that cardiovascular disease is the most common cause of death among patients with fatty liver disease (not liver failure). And we do have randomized controlled trials proving a healthy plant-based diet and lifestyle programs can reverse heart disease––opening up arteries without drugs, without surgery, without stents. Yes, patients with fatty liver disease and fatty hepatitis may indeed eventually develop cirrhosis of the liver, but only if they don’t die of cardiovascular diseases first.

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