Obesity is a complex disorder involving an excessive amount of body fat. Overweight and obesity are prevalent in epidemic proportions in the US and other industrialized nations. The prevalence of obesity was 39.8% and affected about 93.3 million of US adults in 2015~2016 according to the Centers for Disease Control and Prevention(CDC). Obesity isn't just a cosmetic concern, but both overweight and obesity are associated with adverse health consequences, including diabetes, certain cancers, cardiovascular diseases, and degenerative joint disease. Eating disorders such as anorexia and bulimia are much less common but pose major health consequences for affected patients.