Background: Bariatric surgery is currently the only evidence based treatment for morbid obesity. However, we have limited knowledge regarding the mechanism of action in many of procedures used.
Method: This is a review of the results from studies on weight loss, metabolic normalisation and mechanism of action in patients undergoing bariatric surgery.
Results: In the Swedish Obese Subject (SOS) study 2000 patients who underwent bariatric surgery was compared to a conservatively treated matched control group (n=2000). Surgical mortality was 0.25%. The outcome revealed a significant and sustained weight loss of in mean 16% over 1015 years in the whole group (25% after gastric bypass). Furthermore the QoL was improved in operated group as were most cardiovascular risk factors. We also found an adjusted reduction in mortality of 30% in the surgical group and a 40% reduction in cancer incidence in women. Gut hormone release after gastric bypass demonstrates a supraphysiological release of GLP-1, PYY and other gut hormones promoting satiety after test meal, but no increase in fasting state. These effects along with changes in GIP, glucagon, etc. might contribute to weight independent improvements in type 2 diabetes after gastric bypass surgery.
Conclusion: Bariatric surgery, and especially gastric bypass, is associated with substantial and sustained long-term weight loss. This leads to a normalisation of many metabolic risk factors and importantly also reduction in overall mortality and incidence of cancer. The mechanism of action in gastric bypass surgery appears to be complex and includes altered gut hormonal response to a meal.