Why Do People Lose Weight After Metabolic Surgery?

Back in the days, the answer to how bariatric surgery works was rather simple. Mechanistically, you either caused surgical restriction (e.g. vertical banded gastroplasty, adjustable gastric banding) or malabsorption (e.g. jejuno-ileostomy, bilio-pancreatic diversion). 

In the meantime, we know that neither restriction nor malabsorption play a significant role (if any) in why bariatric surgery works. 

Rather, we now believe that the remarkable long-term success of these surgical interventions is based on important metabolic changes induced by these procedures, thus prompting the renaming of bariatric to metabolic surgery.

But what exactly are the metabolic changes induced by the various current procedures, and how do they contribute to the weight loss and other metabolic changes seen in these patients? 

This is now the topic of an extensive review by Alina Akalestou and colleagues, published in Endocrine Reviews

In this paper, the authors discuss what is known about the roles of alterations in the neuroendocrine mechanisms of central appetite control (both wanting and liking), release of gut peptides that change hunger and satiety, as well as change in microbiota and bile acids. 

In addition they briefly review the possibility that metabolic surgery impairs adaptive thermogenesis thereby resulting in a greater metabolic rate than to be expected given the magnitude of weight loss. 

Overall, the mechanisms are clearly manifold and complex and may vary substantially based on the actual surgical procedure but also on the time course following surgery. 

Clearly better understanding these mechanisms should not only inform surgical innovations but also help identify potential pharmacological targets for novel anti-obesity medications. 

Berlin, D