Obesity rates in the US have risen to near epidemic levels. While caloric restriction, exercise, and behavioral modification remain mainstays for the treatment of overweight individuals (BMI 25 to <30), these strategies have not produced sustainable long-term weight loss in the severely obese (BMI≥40). Bariatric surgery has become increasingly popular for the treatment of severe obesity, and has been linked to sustainable weight loss.
A variety of surgical procedures have been used to induce weight loss for severely obese patients. They result in weight loss via different mechanisms: mechanically restricting the size of the stomach, bypassing a portion of the intestines, or by a combination of these mechanisms. Additionally, there is evidence that these procedures generate alterations in gastric and neuropeptides that play a role in weight loss and early satiety.
Currently, the most common procedures performed are done laparoscopically, and they include gastric banding (adjustable gastric band), gastric bypass (Roux-en-Y gastric bypass (RYGB)) and gastric sleeve. The biliopancreatic diversion and vertical banded gastroplasty (VBG) are performed infrequently and are primarily done by select surgeons and centers (specifics of these procedures will not described in detail).
Gastric banding achieves weight loss by creating gastric restriction. The uppermost portion of the stomach is encircled by a band to create a gastric pouch with a capacity of 15 to 30 cc. The band consists of an inflatable doughnut-shaped balloon whose diameter can be adjusted by adding or removing saline via a reservoir port beneath the skin. The bands are adjustable allowing the size of the gastric outlet to be modified, depending on the rate of a patient's weight loss.
Gastric bypass achieves weight loss through a combination of gastric restriction and malabsorption. Reduction of the stomach to a small gastric pouch results in feelings of satiety following even small meals. This small pouch is connected to the lower segment of the small intestine, bypassing the proximal small intestine. Thus, absorptive function is reduced. Possibly also aiding weight loss is the production of unpleasant gastrointestinal symptoms following ingestion of particular foods: symptoms include abdominal pain, cramping, and diarrhea.
Gastric sleeve is a more recently adopted procedure where the stomach is stapled into a tube. This procedure has been gaining interest as it relatively simple to perform and offers a lower post-operative complication rate. It appears to have successful weight loss results and improvements in comorbidities, but longer term results, beyond 5 years, are not yet known.
However, not all patients receive equal benefit from bariatric surgery. Psychosocial factors are commonly cited as important predictors of post-operative outcomes. Many bariatric practices formally screen for mental health conditions during the pre-operative assessment in order to select patients they believe have with the highest likelihood of success; others, including the Veterans Health Administration, do not require formal psychosocial evaluation.
Given the increased interest in surgical weight loss and the desire to select patients who will benefit the most from this intervention, the 3 key questions for this review are as follows:
Key Question 1. What is the prevalence of mental health conditions among bariatric surgery candidates?
Key Question 2. What is the association between pre-operative mental health conditions and bariatric outcomes, including weight loss, quality of life, adherence to behavioral guidelines, risk of suicide, prevalence of mental health conditions, and peri-operative complications?
Key Question 3. Is there evidence to support any pre-operative intervention for patients with mental health disorders to improve post-operative bariatric outcomes, including weight loss?