Hepatic steatosis is the medical term for a fatty liver, a condition where excess fat (primarily triglycerides) builds up inside liver cells. It affects an estimated 38% of the global adult population, making it one of the most common liver conditions in the world. Most people with hepatic steatosis have no symptoms and discover it incidentally during imaging for something else.
How Fat Accumulates in the Liver
Your liver normally processes fats as part of its daily work, packaging them into particles that get shipped out into the bloodstream. Hepatic steatosis develops when that balance tips: more fat flows in than the liver can burn or export. Three things drive this imbalance. First, fat tissue elsewhere in the body releases too many fatty acids into the bloodstream, flooding the liver with raw material. Second, the liver itself ramps up its own fat production, a process called de novo lipogenesis. Third, the liver’s ability to package and export fat as transport particles decreases, trapping triglycerides inside liver cells.
Insulin resistance sits at the center of this process. When cells stop responding normally to insulin, the body compensates by producing more of it. That excess insulin triggers fat tissue to release more fatty acids into circulation while simultaneously flipping on genetic switches inside liver cells that accelerate fat production. Research published in PNAS found that a specific fat byproduct accumulating inside liver cell droplets was responsible for 64% of the variability in insulin sensitivity among study participants, suggesting a reinforcing cycle: insulin resistance drives fat accumulation, and fat accumulation worsens insulin resistance.
Symptoms and How It’s Found
Hepatic steatosis often produces no symptoms at all. When it does, the most commonly reported complaints are fatigue and a general feeling of being unwell. These are vague enough that most people wouldn’t connect them to a liver problem. If the condition progresses to an inflamed state, the liver can swell, which a doctor might detect during a physical exam.
Most cases are caught through routine blood work showing mildly elevated liver enzymes, or through an abdominal ultrasound ordered for unrelated reasons. A more precise tool is a FibroScan, which uses a measurement called a Controlled Attenuation Parameter (CAP) score to estimate how much of the liver contains fat. A CAP score between 238 and 260 dB/m indicates mild steatosis, meaning roughly 11% to 33% of the liver is affected. Scores of 260 to 290 suggest moderate involvement (34% to 66%), and anything above 290 points to severe steatosis affecting more than two-thirds of the liver.
What Causes It
The most common cause by far is metabolic dysfunction, the cluster of conditions that includes obesity, type 2 diabetes, high blood pressure, and abnormal cholesterol levels. You don’t need all of these to develop a fatty liver. Having just one or two significantly raises the risk, especially if you carry excess weight around the midsection.
Heavy alcohol use causes a nearly identical pattern of fat accumulation through a different mechanism. That’s why doctors distinguish between metabolic-related and alcohol-related forms. Other, less common causes include certain medications (like corticosteroids and some cancer drugs), rapid weight loss, and rare genetic conditions that impair fat metabolism.
Updated Terminology
If you’ve encountered confusing overlapping terms for this condition, you’re not alone. For decades, the standard label was non-alcoholic fatty liver disease (NAFLD). In 2023, major liver organizations, including the American Association for the Study of Liver Diseases, adopted new terminology. The condition is now called metabolic dysfunction-associated steatotic liver disease, or MASLD. The more advanced inflammatory stage, previously called NASH (non-alcoholic steatohepatitis), is now MASH. The name change reflects a better understanding that the disease is driven by metabolic dysfunction rather than simply being defined by the absence of alcohol use. You’ll still see the older terms widely used in medical records and older educational material.
When It Becomes Dangerous
Simple hepatic steatosis, fat in the liver without inflammation, is generally considered a reversible and relatively low-risk condition on its own. The concern is progression. In some people, the accumulated fat triggers chronic inflammation, which damages liver cells and produces scar tissue. This scarring (fibrosis) can, over years or decades, advance to cirrhosis, where enough of the liver is scarred that it begins to lose function.
Not everyone progresses. Most people with simple steatosis never develop significant liver damage. But the risk climbs substantially in people with poorly controlled diabetes, persistent obesity, or other metabolic conditions that keep the underlying fat accumulation going unchecked. The inflammatory stage is also associated with higher rates of cardiovascular disease, which is actually the leading cause of death in people with fatty liver disease, not liver failure.
Treatment and Weight Loss Targets
There is no widely prescribed pill that reverses simple hepatic steatosis. The primary treatment is lifestyle change, specifically weight loss. The research on this is unusually precise. Losing at least 5% of your total body weight can measurably reduce liver fat. Losing 7% or more can resolve the inflammatory stage. And losing 10% or more can stabilize or even reverse existing scar tissue. For someone weighing 200 pounds, that translates to 10, 14, or 20 pounds, respectively.
No single diet has proven superior for reducing liver fat, but patterns that improve insulin sensitivity tend to work best. Mediterranean-style eating, which emphasizes vegetables, whole grains, fish, and olive oil while limiting sugar and refined carbohydrates, has the strongest evidence. Regular physical activity helps independently of weight loss by improving insulin sensitivity and reducing the liver’s fat production. Both aerobic exercise and resistance training show benefits.
In 2024, the FDA approved the first medication specifically for the more advanced inflammatory and scarring stage of the disease. This drug, resmetirom (brand name Rezdiffra), works by partially activating thyroid hormone receptors in the liver, which helps the organ burn off stored fat. It is approved only for adults who already have moderate to advanced scarring and is used alongside diet and exercise, not as a replacement for them. It is not indicated for simple steatosis without scarring.
What to Watch For Over Time
If you’ve been told you have hepatic steatosis, the most useful thing you can do is address the metabolic factors driving it. Keeping blood sugar, cholesterol, and blood pressure in healthy ranges matters as much for your heart as for your liver. Periodic monitoring, typically through blood work and sometimes repeat imaging, helps track whether the condition is stable or progressing. Avoiding or minimizing alcohol is generally recommended, since alcohol provides a second independent source of liver stress on top of metabolic fat accumulation.