Obesity refers to an excess amount of body fat. It is a multifactorial medical condition that affects one quarter of U.S. adults and is a risk factor for diabetes, heart disease, stroke, hypertension, gallbladder disease, osteoarthritis, sleep apnea, and some forms of cancer. Orlistat and sibutramine are anti-obesity drugs that have been approved by the FDA. Orlistat exerts its effect by decreasing the amount of fat that the intestine absorbs, while sibutramine increases ones sense of satiety. The purpose of this study is to test the hypothesis that these two drugs in combination, employing different mechanisms of weight control, is a more effective treatment for obesity than either one of the drugs alone. Twelve male Wistar rats weighing between 300-400g were divided into four groups of three animals. The animals in Group 1 were designated as the control group and received neither drug; Group 2 was administered only sibutramine; Group 3 was administered only Orlistat; and Group 4 was administered both Orlistat and sibutramine. The rats were fed a normal diet over the four-week period in which the drugs were administered. Body weight, food intake, blood triglycerides, Lee index, fat-to-lean ratio, resting metabolic rate, and rectal temperature were measured in order to determine the amount of fat absorbed, food intake, weight loss, metabolic rate, and thermogenesis. The results showed significant differences between groups for weight gain, Lee index, and food intake. Overall, the weight gain results supported the hypothesis in that the group receiving both drugs gained the least amount of weight, and therefore the two drugs administered in combination exceeded the anti-obesity effects of either drug alone. The food intake and fat-to-lean ratio results also provided evidence that both drugs together significantly decreased weight gain. The Lee index results, although statistically significant, did not offer any supportive conclusions. Results regarding metabolic rate, thermogenesis, and blood triglycerides were inconclusive. Overall, this study aimed to find a more effective treatment for obesity.