More than 100 million Americans (65% of the adult population) are overweight.  Obesity is the second leading cause of preventable death in the United States after smoking. Annually, obesity-related diseases account for 400,000 premature deaths.
A combination of genetics, environmental issues, and behavioral factors may contribute to the condition. [1, 2] Consumption of high-calorie foods, consumption of too much food, and a sedentary lifestyle all work together to create this condition. Obesity is associated with the development of diabetes mellitus, hypertension, dyslipidemia, arthritis, sleep apnea, cholelithiasis, cardiovascular disease, and cancer. [1, 2] Morbid obesity is defined as severe obesity that threatens one’s health and can shorten lifespan. 
Body mass index (BMI) describes relative weight for height and correlates significantly with an individual’s total body fat.  BMI is based on height and weight and applies to adults of both sexes. BMI is calculated in one of two ways, as follows [1, 3] :
BMI = weight (kg)/(height [m]) 2
BMI = weight (lb)/(height [in.]) 2 × 703
Obesity can be treated medically and surgically. Medical treatment for obesity is difficult, because the amount of weight lost is small and patients tend to regain most of the weight. Operations designed to result in significant and long-lasting weight loss in patients who are severely obese are referred to as bariatric surgery. The term bariatric is derived from the Greek words baros (weight) and iatreia (medical treatment). Laparoscopic gastric bypass surgery, described here, is one such surgical procedure. It involves creating a gastric pouch. [4, 5, 6]
For information on lap band placement (another form of bariatric surgery), see Laparoscopic Lap Band Placement.
In 1991, the National Institutes of Health (NIH) provided a consensus statement for patient selection for bariatric surgery.  Patients were considered candidates for surgery if they met one of the following criteria:
BMI higher than 40
BMI of 35-40 plus one of the following obesity-associated comorbidities: (1) severe diabetes mellitus, (2) pickwickian syndrome, (3) obesity-related cardiomyopathy, (4) severe sleep apnea, or (5) osteoarthritis interfering with lifestyle
To be candidates for bariatric surgery, patients should have attempted, without success, to lose an appropriate amount of weight through supervised diet changes. [7, 6] Patients must also comply with postoperative diet and exercise.
Clinical guidelines on the clinical application of laparoscopic bariatric surgery have been developed by the Society of American Gastrointestinal and Endoscopic Surgeons (SAGES). 
Contraindications for gastric bypass surgery include the following:
History of substance abuse
History of major psychiatric disorder
End-stage organ disease (eg, hepatic, cardiac, pulmonary)
Bariatric surgery is only a tool for weight loss. Patients who are not committed to making long-term lifestyle changes are not ideal candidates for this procedure.
Gill et al compared laparoscopic Roux-en-Y gastric bypass, laparoscopic sleeve gastrectomy, and laparoscopic adjustable gastric banding with respect to effectiveness and safety in 150 consecutive bariatric surgery patients followed for 2 years.  Bypass yielded a greater change in BMI than either sleeve gastrectomy or gastric banding, as well as a greater reduction in obesity-related comorbidities (though all three procedures were judged to be safe).
Rausa et al compared the complications and 30-day mortality of laparoscopic Roux-en-Y gastric bypass with those of the equivalent open procedure.  The meta-analysis and meta-regression analysis included 17 papers published between 2000 and 2014. A higher mortality was noted for open surgery (death rate, 0.82%) than for laparoscopic surgery (death rate, 0.22%). Contemporary reports of LRYGB cite low mortality figures and progressively declining postoperative complication rates for laparoscopic gastric bypasss.
de Raaff et al studied the persistence of moderate or severe obstructive sleep apnea after laparoscopic Roux-en-Y gastric bypass.  They found that predictive factors for such persistence included the following:
Age 50 years or older
Preoperative apnea-hypopnea index 30/hr or higher
Excess weight loss of less than 60%