The purpose of this study was to investigate the effects of wax gourd on weight, triglyceride, leptin and fat cell size in rats fed a high-fat diet. Male Sprague Dawley rats were fed an experimental diet containing total dietary fat at 40% of calories with wax gourd 0%, 5%, 10% and 15% (w/w) for 4 weeks. Weight gain and triglyceride level fell significantly in the 15% wax gourd group compared to the control group. Epididymal fat pad, abdominal fat and perirenal fat tended to decrease in the 15% wax gourd group. Leptin and free fatty acid level were not significantly different among the groups. Fat cell size significantly decreased in the 10% and 15% wax gourd groups compared to the control group. Weight gain correlated positively with visceral fat masses and the levels of leptin and triglyceride. Fat cell size significantly correlated with visceral fat and leptin level. Therefore, the 15% wax gourd diet substantially reduced weight, triglyceride and fat cell size. (Korean J Nutrition 36(5): 446∼451, 2003)