Effects of Bariatric Surgery on Energy Homeostasis

Bariatric surgery represents the most efficient therapy for severe obesity. It reduces the size of fat stores or the amount of body fat gain. The bariatric surgery procedures currently used include Roux-en-Y gastric bypass and sleeve gastrectomy, which are the most commonly performed procedures. Other procedures are laparoscopic adjustable gastric banding and biliopancreatic diversion. The latter represents the most effective surgery for treatment of severe obesity as well as type 2 diabetes. Bariatric surgery reduces energy intake by restricting the size of the stomach reservoir and causing malabsorption, as in the case of biliopancreatic diversion. The present article provides an overview of the literature on the effects of bariatric surgery on energy homeostasis. Accumulated evidence has indicated that the effects of bariatric surgery on energy balance can encompass complex components including effects on the corticolimbic appetitive network, with modulatory effects exerted through changes in gastrointestinal hormones, bile acid production and microbiota composition. The reorganization of the gastrointestinal tract has been shown to reduce the rewarding effects of palatable food and impulsive eating, while elevating anorexigenic hormones glucagon-like peptide 1 and peptide tyrosine tyrosine to stimulate the production of bile acids and normalize the obesogenic gut microbiota. Bariatric surgery could also increase energy expenditure, which represents, like energy intake, a key component of the energy balance equation.