Oolong tea (Camellia sinensis) has been investigated for its potential benefits in metabolic health, including fatty liver disease (specifically non-alcoholic fatty liver disease, NAFLD). Several animal studies have reported that oolong tea extracts may reduce hepatic fat accumulation, improve lipid metabolism, and suppress oxidative stress and inflammation in the liver. These effects are largely attributed to its polyphenols, particularly catechins and theaflavins, which exhibit antioxidant and anti-inflammatory properties. For example, studies in mice fed a high-fat diet have shown that oolong tea extract can attenuate liver steatosis and improve markers of liver function.

However, direct clinical evidence in humans is limited. Some epidemiological studies suggest that regular tea consumption (including oolong) is associated with a lower risk of developing NAFLD, but these studies often group different types of tea together, making it difficult to attribute effects specifically to oolong tea. There are very few, if any, randomized controlled trials specifically evaluating oolong tea's effects on fatty liver disease in humans.

In summary, while there is some scientific rationale and preclinical evidence supporting the potential benefits of oolong tea for fatty liver disease, the evidence is preliminary and mostly based on animal models. Human clinical data are lacking, and therefore, the evidence rating remains low.