Hepatic steatosis is the medical term for a fatty liver. It means fat droplets, primarily triglycerides, have built up inside your liver cells beyond normal levels. If you saw this term on an imaging report or lab results, it’s telling you that your liver is storing more fat than it should be. About 25% of adults in the U.S. have some degree of fatty liver disease, making it one of the most common liver conditions.
What’s Happening Inside Your Liver
Your liver normally processes and exports fat as part of its daily work. In hepatic steatosis, that balance breaks down. Fat arrives at the liver faster than the liver can package and send it out, or the liver itself ramps up fat production. The result is triglycerides accumulating inside liver cells, stored in distinct droplet structures surrounded by a thin membrane.
Interestingly, this fat buildup may not be purely harmful at first. Research suggests that storing triglycerides in these droplets can actually serve a protective function by sequestering free fatty acids, which are more toxic to liver cells when left floating around. The problem comes when fat accumulation becomes excessive or persists long enough to trigger inflammation.
Grades of Fatty Liver
Not all fatty livers are equally fatty. Doctors grade steatosis on a scale from S0 to S3 based on how much of the liver is affected:
- S0: No significant steatosis
- S1 (mild): Roughly 11% to 33% of liver tissue contains fat
- S2 (moderate): About 34% to 66% fat involvement
- S3 (severe): More than 67% of the liver is fatty
If your report mentions a grade, it’s placing you somewhere on this spectrum. Mild steatosis is extremely common and often discovered incidentally during imaging for something else entirely.
Why Fat Builds Up in the Liver
The strongest driver of hepatic steatosis is insulin resistance, the condition where your cells stop responding efficiently to insulin. When insulin signaling goes wrong, fat tissue releases more fatty acids into the bloodstream, and the liver struggles to manage the flood. This is why fatty liver overlaps so heavily with metabolic conditions like type 2 diabetes, obesity (especially belly fat), high triglycerides, and high blood pressure.
You don’t need to be severely overweight to develop it. People with even one cardiometabolic risk factor, such as a fasting blood sugar above 100 mg/dL, triglycerides above 150 mg/dL, or a BMI over 25, can qualify for the diagnosis. Genetics also play a role: some people accumulate liver fat more readily than others on the same diet.
Alcohol is the other major cause. Heavy drinking can produce an identical pattern of fat buildup. Doctors now use the umbrella term “steatotic liver disease” to cover all causes, with “metabolic dysfunction-associated steatotic liver disease” (MASLD) replacing the older term NAFLD for cases tied to metabolic factors rather than alcohol.
Updated Terminology You May See
The medical world recently overhauled the naming system for fatty liver disease. If you’ve seen conflicting terms, here’s what maps to what:
- NAFLD (nonalcoholic fatty liver disease) is now called MASLD (metabolic dysfunction-associated steatotic liver disease)
- NASH (nonalcoholic steatohepatitis) is now called MASH (metabolic-associated steatohepatitis)
- MetALD is a new category for people who have metabolic risk factors and also drink moderate-to-heavy amounts of alcohol
The shift was led by the American Association for the Study of Liver Diseases, partly because “nonalcoholic” defined the condition by what it wasn’t rather than what it was, and partly to reduce stigma. Your doctor may still use the older terms, but newer reports will increasingly use MASLD and MASH.
Does It Always Get Worse?
For most people, no. Simple steatosis, meaning fat in the liver without significant inflammation or cell damage, typically does not progress to serious liver disease. The American Liver Foundation notes that the majority of people with MASLD have this simpler form.
About 20% of people with MASLD do develop MASH, the inflammatory stage where liver cells become damaged and scarring begins. Why some people progress and others don’t isn’t fully understood, though genetics appear to play a role. MASH can eventually lead to significant scarring (fibrosis) and, in a smaller subset, cirrhosis. But this progression usually takes years to decades, not months.
The bigger immediate concern with hepatic steatosis isn’t liver failure. It’s what fatty liver signals about your cardiovascular health. The same metabolic dysfunction driving fat into your liver also raises your risk for heart disease, which is actually the leading cause of death in people with MASLD.
How It’s Detected
Hepatic steatosis is usually found through imaging rather than symptoms, since fatty liver rarely causes noticeable problems until it’s advanced. The most common methods differ in accuracy.
Standard ultrasound is widely available and performs well for detecting any steatosis at all. MRI-based fat measurement (called MRI-PDFF) is the most accurate tool across all grades, with near-perfect detection for mild steatosis and strong accuracy for moderate and severe cases. A meta-analysis found MRI-PDFF outperformed the FibroScan device (which uses a vibration-based measurement called CAP) for grading moderate and severe steatosis. In practice, your doctor will likely start with ultrasound or FibroScan and reserve MRI for cases where precise fat quantification matters.
Reversing Liver Fat
Hepatic steatosis is one of the more reversible conditions in medicine. Losing 5% or more of your body weight has been shown to meaningfully reduce liver fat. For someone weighing 200 pounds, that’s 10 pounds. Greater weight loss brings greater benefit, with 7% to 10% loss associated with improvement in inflammation and early scarring for those who have progressed beyond simple steatosis.
No specific diet is proven superior, but the Mediterranean dietary pattern (rich in olive oil, fish, vegetables, and whole grains) has the most consistent evidence behind it. Regular physical activity helps reduce liver fat even without significant weight loss on the scale, likely because exercise improves insulin sensitivity directly.
On the medication front, the FDA approved semaglutide (Wegovy) for treating MASH with moderate-to-advanced scarring. In clinical trials, 63% of participants on the drug achieved resolution of their liver inflammation without worsening scarring, compared to 34% on placebo. This approval was specifically for the more advanced inflammatory stage, not simple steatosis, which is still managed primarily through lifestyle changes.
What a Diagnosis Means for You
If your report says hepatic steatosis, it’s worth treating as a useful early warning rather than an urgent crisis. It means your metabolism is pushing fat into your liver, and the same forces are likely affecting your blood vessels and heart. The practical next steps are straightforward: get your blood sugar, cholesterol, and blood pressure checked if they haven’t been recently, and focus on the weight loss and activity changes that can pull fat back out of your liver. For the large majority of people, simple steatosis stays simple and responds well to these changes.