The purpose of this protocol is to investigate the effect of treatment with the study drug, called lorcaserin on centers of the brain that control appetite and food intake, as well as lorcaserin's other metabolic effects. Lorcaserin's effect on the brain will be investigated using functional magnetic resonance imaging (fMRI). Lorcaserin was approved in June 2012 as an addition to a reduced-calorie diet and exercise, for chronic weight management. Previous weight loss drugs, such as fenfluramine, acted throughout the body and caused heart problems. Lorcaserin is different because it only acts on receptors (sites of action) that are found in the brain and does not act on the heart, and thus, has not been shown to cause the heart problems seen in the past.