Obesity is currently a major threat to the health of people all over the world. This condition is a risk factor for cardiovascular diseases, diabetes, and certain types of cancer. This study concerned with the use of Broussonetia luzonicus leaves to prevent the development of obesity in male Swiss mice. Broussonetia luzonicus leaves were collected from Nueva Vizcaya, Philippines. The leaves were air-dried and extracted using a percolator and the concentrated under reduced pressure to obtain the crude methanolic extract. Obesity was induced by feeding them the mice with high caloric diet. Twenty-five mice were divided into 5 groups namely, negative control, positive control which is orlistat, 1000mg/kg, 1500 mg/kg, and 2000 mg/kg of the crude methanolic extract of B. luzonicus leaves. The crude methanolic extract was administered using an oral gavage for 28 days, weights were collected every 7 days, and in the last day, the epididymal fats were collected, stained and viewed under a microscope. The size of the adipocytes were measured using the software image J version 1.49. The size of the adipocytes were statistically analyzed using ANOVA with scheffe as the post-hoc analysis. The results showed that the weight measurements were inconsistent which may be due to the young age of the test animals. The reduction of adipocyte size indicated that there is no significant difference among the positive control, 1000 mg/kg, 1500 mg/kg, and 2000 mg/kg dose of the methanolic extract from which can be concluded that the methanolic extracts of B. luzonicus leaves is just as effective as orlistat in decreasing adipocyte size.