Researchers tested whether a Mediterranean diet or a low-fat diet worked better for treating fatty liver disease in 250 adults over 12 weeks. Both diets reduced liver fat, liver stiffness, and body weight by similar amounts. Interestingly, a genetic variation that some people carry didn’t change how well either diet worked. This suggests that what matters most for improving fatty liver disease is losing weight through diet—and people can choose whichever healthy eating plan they’ll actually stick with.

The Quick Take

  • What they studied: Whether a Mediterranean diet (lots of vegetables, olive oil, fish) or a low-fat diet works better for treating fatty liver disease, and whether a person’s genes affect which diet works best for them.
  • Who participated: 250 adults with fatty liver disease and overweight (BMI of 25 or higher). People with heavy alcohol use or other liver problems were excluded.
  • Key finding: Both diets worked equally well. After 12 weeks, both groups reduced liver fat by similar amounts, improved liver stiffness, and lost about the same amount of weight. A genetic variation called PNPLA3 didn’t make one diet better than the other for any group.
  • What it means for you: If you have fatty liver disease, you don’t need to stress about choosing between Mediterranean or low-fat diets—both can help. The key is picking one you can actually follow long-term and losing weight. Talk to your doctor before starting any diet, especially if you have liver disease.

The Research Details

This was a randomized controlled trial, which is one of the strongest types of research. Researchers randomly assigned 250 adults with fatty liver disease into two groups: one followed a Mediterranean diet and the other followed a low-fat diet. Both diets provided fewer calories than people normally eat (to encourage weight loss). The study lasted 12 weeks, with measurements taken at the start and end.

All participants received actual food items to help them stick to their assigned diet, and researchers tracked how well people followed the plan using questionnaires. Doctors measured liver health using special ultrasound techniques that show how much fat is in the liver and how stiff the liver tissue is—both signs of liver damage. Researchers also collected blood tests and body measurements.

Before the study started, researchers tested everyone’s genes to see who carried a specific genetic variation (PNPLA3) that some people inherit. This allowed them to check whether this genetic difference changed how well each diet worked.

This research design is important because it compares two diets head-to-head in a fair way. By randomly assigning people to groups and providing actual food, researchers could see real results rather than just asking people what they eat. Testing genes adds another layer of understanding—it shows whether personalized medicine based on genetics might help, or whether one-size-fits-all advice works fine.

This study has several strengths: it’s a randomized controlled trial (the gold standard), it included a decent number of participants (250), researchers provided actual food to improve accuracy, and they used validated measurement tools for the liver. However, the 12-week timeframe is relatively short, so we don’t know if benefits last longer. The study also excluded people with heavy alcohol use, so results may not apply to everyone with fatty liver disease.

What the Results Show

Both diets significantly improved fatty liver disease markers. The Mediterranean diet group and low-fat diet group showed nearly identical improvements in liver fat content (measured by CAP score), with no meaningful difference between them. Liver stiffness—a sign of scarring—also improved equally in both groups.

Weight loss was similar between groups, with both losing weight on average. The Mediterranean diet group lost slightly more weight (about 3 kg difference), but this difference was small enough that it could have happened by chance.

The results were consistent across all the measurements doctors used. Whether researchers looked at liver fat, liver stiffness, or weight loss, both diets performed essentially the same. This consistency strengthens confidence in the findings.

The genetic variation (PNPLA3) that researchers tested did not affect how well either diet worked. Some people carry a genetic variant that makes them more prone to fatty liver disease, but this didn’t change whether they responded better to Mediterranean or low-fat eating. This is important because it suggests that genetic testing might not be necessary to choose between these diets—both work regardless of your genes.

Previous research has shown that both Mediterranean and low-fat diets can help with fatty liver disease, but it wasn’t clear if one was significantly better. This study confirms that they’re roughly equivalent. The finding about PNPLA3 genetics is particularly valuable because earlier research suggested genetics might play a bigger role in diet response than this study found. This suggests that weight loss itself—regardless of diet type—may be the most important factor.

The study only lasted 12 weeks, so we don’t know if benefits continue or fade over months or years. The study excluded people with heavy alcohol use, so results may not apply to them. The sample size, while reasonable, could have been larger for more confident conclusions. Additionally, the study didn’t track what people ate after the 12 weeks ended, so we don’t know about long-term adherence or sustained benefits.

The Bottom Line

If you have fatty liver disease, either a Mediterranean diet or a low-fat diet can help improve your condition. The most important factor is choosing one you can stick with long-term and achieving weight loss. Moderate calorie reduction (eating somewhat less than usual) appears effective. Confidence level: Moderate to High—this is based on a well-designed study, though longer-term research would strengthen these conclusions.

This research applies to adults with fatty liver disease who are overweight. It’s particularly relevant for people trying to decide between popular diet approaches. However, this study excluded people with heavy alcohol use or other liver disease causes, so if you fall into those categories, talk with your doctor about what’s best for you. Anyone with liver disease should consult their healthcare provider before making major diet changes.

In this study, improvements in liver health appeared within 12 weeks. However, you might not feel different—fatty liver disease often has no symptoms. Realistic expectations: noticeable weight loss within 4-8 weeks, measurable liver improvements within 8-12 weeks, but long-term success requires maintaining the diet for months or longer.

Want to Apply This Research?

  • Track weekly weight and weekly adherence to your chosen diet (Mediterranean or low-fat) using a simple yes/no checklist. This mirrors what the research showed was important: consistent diet adherence and weight loss.
  • Choose either Mediterranean diet principles (vegetables, olive oil, fish, whole grains) or low-fat diet principles (lean proteins, low-fat dairy, whole grains, limited oils) based on which feels more sustainable for you. Use the app to log meals and track which diet pattern you’re following, rather than obsessing over specific foods.
  • Set a goal to lose 5-10% of your body weight over 3 months (similar to the study timeline). Track weight weekly and diet adherence daily. If you have access to liver ultrasound measurements through your doctor, compare results every 3 months. Focus on consistency rather than perfection—the study showed that steady adherence matters more than diet type.

This research suggests that both Mediterranean and low-fat diets may help improve fatty liver disease, but it is not medical advice. Fatty liver disease can be serious and requires professional medical evaluation. Before starting any new diet, especially if you have liver disease, consult with your doctor or a registered dietitian. This study lasted only 12 weeks, so long-term effects are unknown. Individual results vary, and what works for one person may not work for another. If you have symptoms like abdominal pain, jaundice, or unusual fatigue, seek immediate medical attention.