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. 

Gastric bypass, also known as Roux-en-Y Gastric Bypass. This is the favored weight-loss surgery because it has shown greater long-term weight loss and improvement of complications, such as type 2 diabetes, than gastric banding. The reduced size of the stomach allows for reduced consumption of food by the patient, which in turn, results in gradual weight loss. In gastric bypass (Roux-en-Y gastric bypass), the surgeon creates a small pouch at the top of your stomach. The small intestine is then cut a short distance below the main stomach and connected to the new pouch. Food and liquid flow directly from the pouch into this part of the intestine, bypassing most of your stomach. Serious risks from the surgery include blood clots and the need for reoperation. People with higher BMIs and those who aren't able to walk 200 feet (61 meters) or who have a history of obstructive sleep apnea have a higher risk of complications.11