Six-week tomato diet reduces liver fat marker in MASLD trial without weight loss

A six-week trial in Italy found something unexpected: people who ate tomatoes every day showed measurable improvement in liver fat accumulation, even though they didn't lose weight. The study, published in Nutrients, involved 79 adults with metabolic dysfunction-associated steatotic liver disease—a condition where fat builds up in the liver without heavy alcohol use—and tracked what happened when half of them ate 200 grams of raw tomatoes plus 50 grams of tomato sauce daily while the other half avoided tomatoes entirely.

Metabolic dysfunction-associated steatotic liver disease, or MASLD, is now the most common chronic liver disease worldwide. It develops alongside obesity, insulin resistance, and metabolic problems, and the fat that accumulates in the liver can trigger inflammation and oxidative stress that eventually leads to scarring, cirrhosis, or cancer. Current treatment focuses on lifestyle changes, particularly diet, but most guidance emphasizes overall eating patterns and weight loss. What's missing is clarity about whether specific foods might help reduce liver fat on their own, independent of dropping pounds.

Tomatoes have long been central to the Mediterranean diet, which research links to better liver health and metabolic function in MASLD patients. They contain lycopene and other antioxidant compounds that, in laboratory studies, appear to reduce inflammation and oxidative stress—two drivers of liver damage. The catch is that most evidence comes from observation, not controlled trials. No one had rigorously tested whether eating more tomatoes actually changes liver fat in people with MASLD.

The Italian researchers recruited adults aged 18 to 65 with confirmed MASLD and at least one cardiometabolic risk factor. They excluded anyone drinking heavily or with other liver diseases. Of 415 people who filled out an initial questionnaire, 88 qualified, and 79 completed the study. The tomato group ate their daily portion of fresh and cooked tomatoes sourced from a certified producer using standardized hydroponic methods to ensure consistency. The control group ate no tomatoes. Both groups were told to keep everything else about their diet and lifestyle the same.

The results were striking in their specificity. Liver fat, measured by a technique called controlled attenuation parameter—essentially an ultrasound-based scan that estimates how much fat is in the liver—dropped by a median of 35 units in the tomato group and 18 units in the control group. That difference was statistically significant. But here's what didn't change: body weight stayed stable in both groups. Waist circumference, total body fat, visceral fat, blood sugar control, cholesterol, inflammatory markers, liver enzymes—all remained essentially flat. The tomato eaters didn't lose weight, yet their livers accumulated less fat.

The researchers were careful about what they claimed. This was an exploratory trial with a small sample, run at a single center, for only six weeks. They didn't measure lycopene or carotenoid levels in participants' blood to confirm people were actually absorbing the compounds. They didn't assess whether the improvement in liver fat would translate to real clinical benefit—whether it would prevent fibrosis or cancer down the line. Participants knew they were eating tomatoes, which could have influenced how they reported their diet. The CAP reduction, while measurable, might not matter clinically.

Still, the finding points toward something worth pursuing: a common food that appears to influence liver fat through mechanisms separate from weight loss. For people with MASLD who struggle to lose weight, or who have lost weight without fully resolving their liver disease, tomatoes might offer a modifiable lever. But the authors are clear that larger, longer trials are needed before anyone should treat this as established fact. The study is hypothesis-generating, not hypothesis-confirming. It suggests a direction for research, not a treatment protocol.