Effectiveness of surgery

Weight loss
In general, the malabsorptive procedures lead to more weight loss than the restrictive procedures however, have a higher risk profile. A meta-analysis from University of California, Los Angeles reports the following weight loss at 36 months:
Biliopancreatic diversion - 53 kg
• Roux-en-Y gastric bypass (RYGB) - 41 kg
o Open - 42 kg
o Laparoscopic - 38 kg
• Adjustable gastric banding - 35 kg
• Vertical banded gastroplasty - 32 kg
More recent studies have demonstrated that the medium (3–8 years) and long term (>10 years) weight loss results for RYGB and LAGB become very similar. However, the range of excess weight loss for LAGB patients (25% to 80%) is much broader than that of RYGB patients (50% to 70%). Data (beyond 5 years) for Sleeve Gastrectomy is not yet available (as of 12/09).

Reduced mortality and morbidity
Several recent studies report decrease in mortality and severity of medical conditions after bariatric surgery. But long term effects are not clear. In the Swedish prospective matched controlled trial, patients with a body mass index (BMI) of 34 or more for men and 38 or more for women underwent various types of bariatric surgery and were followed for an average of 11 years. Surgery patients had a 23.7% reduction in mortality (5.0% vs. 6.3% control, adjusted hazard ratio 0.71). This means 75 patients must be treated to avoid one death after 11 years (number needed to treat is 77).

In a Utah retrospective cohort study that followed patients for an average of 7 years after various types of gastric bypass, surgery patients had 0.4% mortality while control patients had 0.6% mortality. Death rates were lower in the gastric bypass patients for all diseases combined, as well as for diabetes, heart disease and cancer. Deaths from accident and suicide were 58% higher in the surgery group.
A randomized, controlled trial in Australia compared laparoscopic adjustable gastric banding ("lap banding") with non-surgical therapy in 80 moderately obese adults (BMI 30-35). At 2 years, the surgically-treated group lost more weight (21.6% of initial weight vs. 5.5%) and had statistically significant improvement in blood pressure, measures of diabetic control, and high-density lipoprotein cholesterol.. Post surgical complications included 1 patient with an infected surgical site, 4 with lap band malpositioning requiring laparoscopic revision, and 1 patient with cholecystitis. In the non-surgical group, 12 patients declined or did not tolerate orlistat or diet restrictions, and 4 patients developed acute
cholecystitis.
Bariatric surgery in older patients has also been a topic of debate, centered on concerns for safety in this population. One study of elderly patients undergoing laparoscopic bariatric surgery at Mount Sinai Medical Center, however, reported 0% conversion to open surgery, 0% 30-day mortality, 7.3% complication rate, and average hospital stay of 2.8 days. post operative mortality from 0.1 - 2 %
Laparoscopic bariatric surgery requires a hospital stay of only one or two days. Short-term complications from laparoscopic adjustable gastric banding are reported to be lower than laparoscopic Roux-en-Y surgery, and complications from laparoscopic Roux-en-Y surgery are lower than conventional (open) Roux-en-Y surgery.

Adverse effects

Complications from weight loss surgery are frequent. A study of insurance claims of 2522 who had undergone bariatric surgery showed 21.9% complications during the initial hospital stay and a total of 40% risk of complications in the subsequent six months. This was more common in those over 40 and led to increased health care expenditure. Common problems were gastric dumping syndrome in about 20% (bloatedness and diarrhoea after eating, necessitating small meals or medication), leaks at the surgical site (12%), incisional hernia (7%), infections (6%) and pneumonia (4%). Mortality was 0.2%. As the rate of complications appears to be reduced when the procedure is performed by an experienced surgeon, guidelines recommend that surgery is performed in dedicated or experienced units.