Fact-checked by Dr. Anthony Gustin, DC, MS.
Written by Emily Ziedman
Historically, liver damage has come from alcoholism — too much drinking makes your liver accumulate fat, which can eventually shut it down.
But with the recent rise in obesity, a new type of liver damage has become far too common: non-alcoholic fatty liver disease (NAFLD). NAFLD usually stems from an unhealthy diet, which causes fat to gradually build up to dangerous levels in your liver. Today, about one in three Americans has NAFLD[*].
The good news is that NAFLD is both preventable and reversible, and with a few diet and lifestyle changes, you can get your liver back to good shape.
This article will tell you everything you need to know about fatty liver disease: what it is, why it happens, and what you can do to prevent it (or reverse it).
Fatty liver disease is exactly what it sounds like: you accumulate too much fat in your liver.
It’s normal for your liver to store some fat. You can use stored liver fat to make energy when you’re low on fuel.
The problem arises when fat creeps up to more than 5% of your liver’s weight. That’s considered fatty liver disease.
There are two main types of fatty liver disease:
- Alcoholic fatty liver disease, which is caused by too much alcohol, and
- Non-alcoholic fatty liver disease (NAFLD), which is due to lifestyle and diet
If you don’t deal with NAFLD, it can progress further to a more serious condition called non-alcoholic steatohepatitis (NASH).
You can think of NAFLD as a warning sign. You have excess fat in your liver, but there’s no scarring and little to no inflammation present. Simple NAFLD typically won’t damage your liver[*].
But if you don’t address NAFLD and it keeps getting worse, you could end up with NASH. This is where things get ugly.
With NASH, your liver becomes inflamed and starts to scar, and your liver cells begin to die off. This inflammation and damage can lead to cirrhosis or liver cancer[*]. Between 7-30% of people with NAFLD develop NASH[*].
Researchers don’t know the exact mechanism behind NAFLD. What they do know is that it’s linked to a bunch of different metabolic issues, including insulin resistance, diabetes, obesity, high triglycerides (fat in the blood), and high cholesterol[*].
Diet and exercise play a big role in NAFLD, as do genetic factors. Your gut bacteria may influence your liver health, too.
#1: Diet and Fatty Liver Disease
Sugar seems to be one of the biggest drivers of NAFLD. Fructose — the sugar found in fruit and high fructose corn syrup — is especially hard on your liver, and one of the biggest dietary drivers of liver fat storage[*].
Combining sugar and saturated fat is even worse (although saturated fat alone is okay for your liver — more on that later)[*].
Sugar causes your blood glucose to spike, and your body releases insulin to draw the glucose out of your blood and store it as glycogen. But your glycogen stores are only so big — if you eat a lot of sugar and fill up your glycogen stores, your liver turns the extra glucose into fat.
If you’re healthy, that extra fat gets shuttled along to your fat cells for storage. You end up gaining weight, but at least it goes to the right place.
But if you eat too much sugar (or sugar and fat together) for too long, you become insulin resistant.
Insulin resistance means your body doesn’t read insulin signaling properly and ends up dumping stored fat back into your bloodstream. Then your body panics and sends that fat to your liver [*][*]. Insulin resistance from eating a poor diet seems to be one of the major causes of NAFLD[*].
Fructose has its own special transporter (think of it as a door) outside the cells in your gut.
When you’re healthy, you don’t absorb more fructose than you can handle. But if you eat too much fructose on a regular basis, your cells create more transporters, and you start letting more and more fructose into your liver[*][*]. That’s when you start developing NAFLD.
#2: Exercise and Fatty Liver Disease
Exercise (or lack of it) also plays a big role in NAFLD. Working out decreases the amount of fat your liver holds on to[*]. It also lowers your blood sugar and improves your insulin sensitivity.
That means hitting the gym both decreases existing liver fat and makes it less likely that you’ll accumulate more of it in the future.
Working out also helps you burn body fat. Obesity is a risk factor for NAFLD, and there’s a strong correlation between weight loss and liver health[*].
#3: Genetics and Fatty Liver Disease
Some genetic variants also increase your risk of NAFLD, while others make NAFLD more likely to progress to NASH, the version of NAFLD that causes liver inflammation and damage[*].
You can get a genetic test to see if you’re predisposed to have NAFLD. Even if you are, though, diet and exercise should keep your liver healthy[*].
#4: Gut Microbiome and Fatty Liver Disease
Your gut bacteria also affect your risk of fatty liver disease.
If your gut bacteria get out of balance, your gut can become overrun by harmful bacteria. Bad gut bacteria produce endotoxins to kill off competing bacteria.
Diet is one of the best ways to keep your gut microbiome balanced. Fiber, in particular, feeds your good bacteria and can help protect against bad bacteria[*].
Avoid sugar, too — a study in mice found that switching from a high-fiber diet to a high-sugar diet shifted the microbiota in a single day to favor the endotoxin rich bad bacteria[*].
If you change your lifestyle, you can get your liver to burn through stored fat and reverse fatty liver disease.
Weight gain is a major risk factor for NAFLD. Weight loss, on the other hand, is one of the best things you can do to improve overall liver function, NAFLD, and NASH. This is particularly true if you are obese or have type 2 diabetes[*][*].
However, weight loss alone may not be the key. Research suggests that it’s not just losing extra pounds, but how you lose them that counts.
Diet and lifestyle factors like exercise and avoiding high fructose corn syrup play a huge role in your overall chances of reversing fatty liver[*]
And a diet that optimizes your gut microbiome is important for overall metabolic health and conditions related to NAFLD, like diabetes and heart disease[*].
On a low-carbohydrate ketogenic diet, you eat very few carbs and get the majority of your calories from fat and protein.
As you learned earlier, insulin and carbohydrates play a key role in the progression of fatty liver. A high-carbohydrate, low-fat diet can worsen fatty liver, especially if you’re eating a lot of sugar.
But what about all that dietary fat you eat when you’re following a ketogenic diet? Could a high-fat diet lead to fatty liver?
According to a few recent studies, the answer is no.
Most of the fat that accumulates in your liver comes from de novo lipogenesis (DNL). DNL occurs when your body creates fat from excess carbohydrates or protein[*].
There’s no shortage of research showcasing the benefits of a low-carb diet for liver and metabolic health. Here are a few highlights:
- One study found that six months of a ketogenic diet led to significant weight loss and improvement of fatty liver disease in obese patients[*]. At the end of six months, patients lost an average of 28 pounds and significantly reversed their liver inflammation and damage.
- In another study, healthy patients following a low-carbohydrate diet saw a significant decrease in liver fat in just 10 days[*].
- In a third study, two weeks on a ketogenic diet caused a 42% decrease in liver fat in people with NAFLD[*].
- Still more studies confirm the potential benefits of following a ketogenic diet and markers for metabolic syndrome, including NAFLD[*].
- And finally, a randomized clinical trial of 45 patients with NAFLD revealed that following a low-carbohydrate diet had a beneficial impact on liver enzymes as well as serum fibrinogen, a protein that is typically high in more severe forms of NAFLD[*].
With the carbohydrate restriction of a keto diet, you don’t have sugar or fructose that can turn into liver fat. In addition, you’re safeguarding against insulin resistance, which further protects against fatty liver.
If you want to give keto a try, check out this complete guide to starting keto in just 30 days.
In addition to a keto diet, there are some specific foods that help with NAFLD.
Walnuts. Walnuts improved liver function tests and show therapeutic potential for people with NAFLD. They reduce both liver fat and inflammation[*].
Avocados. A randomized controlled study found that eating monounsaturated fat (like in avocados) reduced liver fat. Avocados specifically had lipid-lowering, antioxidant, and anti-inflammatory effects in those with NAFLD[*][*].
Coffee. Drinking coffee every morning reduces risk of NAFLD, and decreases NASH severity[*].
Fatty fish. A meta-analysis found that omega-3s improved both NAFLD and NASH, and decreased blood triglycerides[*]. You can get lots of omega-3s from salmon, sardines, anchovies, and other fatty coldwater fish, or you can take a fish oil or krill oil supplement.
Green tea. The catechins in green tea may help reduce oxidative stress to the liver and improve liver fat and inflammation[*].
Whey protein. A randomized controlled study found that taking whey protein daily decreased liver fat in obese females[*].
Vitamin D. Vitamin D deficiency contributes to insulin resistance, metabolic syndrome, and NAFLD[*]. You synthesize vitamin D from direct sun exposure on your skin, and because most of us spend our days inside and clothed, you likely aren’t getting enough vitamin D.
You can either take a vitamin D supplement or spend 10-15 minutes a day in the sun with as little clothing on as possible. You don’t want sunscreen (it blocks vitamin D synthesis), but you also don’t want to burn. A little sunlight is good. Too much (i.e., getting a sunburn) will increase your cancer risk.
Milk thistle. Milk thistle decreases liver inflammation in people with NAFLD[*].
Takeaway: The Keto Diet Does Not Cause Fatty Liver Disease
With the right diet and lifestyle changes, you can prevent or reverse fatty liver disease and keep your liver running strong throughout your entire life.
If you have NAFLD or NASH, try switching to a ketogenic diet, and work out at least three times a week.
At the very least, cut down on sugar, and be especially careful about products that contain high-fructose corn syrup. Your liver will likely start to get better within a few weeks.