The World Health Organization (WHO) and the U.S. National Institutes of Health define obesity as a chronic disease of multifactorial etiology characterized by abnormal or excessive accumulation of fat that is detrimental to health, a patient is considered obese when his or her body mass index (BMI) is ≥ 30 kg/m².

Bariatric surgery is a set of surgical procedures aimed at reducing weight and obesity-related comorbidities.

Bariatric surgery (BS) is the most effective treatment alternative to achieve significant and sustained long-term weight reduction in patients with obesity. The reduction of excess body weight obtained with surgical treatment allows better control of diseases that constitute risk factors for long-term cardiovascular morbidity and mortality such as DM2, arterial hypertension and dyslipidemias.

In DM2, studies demonstrate a significant and sustained long-term improvement in disease control in 50 to 70% of patients. The improvement in metabolic control in DM2 is directly proportional to the weight reduction achieved with different surgical procedures.

The results of controlled clinical trials have shown that surgical treatment of obese patients with DM2 allows better control of glycemia and cardiovascular risk factors, less use of medications and higher remission rates compared to the different medical treatment alternatives.

Surgical procedures for the treatment of obesity have been classified as restrictive, malabsorptive and mixed, according to the mechanism by which they help to control excess body weight.

According to this classification, vertical gastrectomy would be considered a restrictive procedure and gastric bypass a mixed procedure since it combines a restriction of food intake with the creation of a very small stomach and a decrease in caloric absorption due to the absence of contact of nutrients in part of the proximal intestine.

More recent studies have shown that the anatomical changes associated with the different surgical procedures induce physiological changes that would be largely responsible for the effective control of excess body weight. 

These mechanisms include modifications in the secretion of gastrointestinal hormones, in the metabolism of bile acids and in the intestinal microbiota, among others. These entero-hormonal changes would be especially important in the control of metabolic alterations secondary to obesity, highlighting the improvement in regulatory mechanisms of glucose homeostasis and, in the long term, maintaining control of excess body weight.