Bariatric surgery: is a matter of cutting calories or cutting metabolic regulators?

Nowadays obesity represents one of the most important chronic disease all over the world. With the increasing obesity prevalence, an increasing spread of bariatric surgery could also be attended. Bariatric surgery showed to be the most efficient treatment not only to maintain weight loss in the long-term but also to improve the metabolic complications associated to obesity. A very discussing topic regards the causes of superiority of bariatric surgery over medical treatment. This superiority can be explained by two main hypotheses: first, bariatric surgery produces a greater weight loss and thus improves metabolism by cutting calories with restriction and/or malabsorption; second, surgery acts through metabolic regulators that are beyond mechanisms linked to weight loss and caloric restriction per se. In this review, we briefly analyze the different mechanisms sustaining the efficacy of bariatric surgery, concentrating our attention on the most recent discoveries and comparing the changes occurring after surgery with those obtained by a low caloric diet.