People in the Mediterranean region have long used olive tree leaves as part of their diet and in traditional medicines.

Olive leaves contain several key polyphenols, such as oleacein and oleuropein. Polyphenols occur naturally in plants, and research suggests that they may help protect against a range of conditions, such as  heart disease and cancer.

These polyphenols may underlie some of the potential health benefits of olive leaf extract.

In this article, we discuss some of these health benefits, as well as the evidence to support them. We also cover dosage and possible side effects.Weight gain

Olive leaf extract hydroxytyrosol is available as a supplement.

Olive tree leaves contain oleuropein and hydroxytyrosol which is a polyphenol that may help prevent weight gain.

In a 2016 study  researchers orally administered oleuropein to rats withobesity that were

consuming a high-cholesterol diet. After 8 weeks, the rats had a lower body weihgt, less fat tissue, and an improved metabolic profile.

Another study from 2014,found that oleuropein supplementation reduced body weight and weight gain in mice that were consuming a high-fat diet.

These findings suggest that olive leaf extract containing oleuropein may have the potential to reduce weight gain and lower the risk of obesity.

However, further studies are necessary to confirm this possible health benefit in humans.