The drug being tested in this study is called naltrexone HCl/bupropion HCl (NB). NB is approved by the U.S. Food and Drug Administration (FDA) in addition to a reduced-calorie diet and increased physical activity for chronic weight management in adults who are obese or who are overweight and have at least one additional weight-related condition such as high blood pressure, diabetes or high cholesterol. This study is conducted to determine the potential effect of NB relative to placebo on cardiac repolarization.