# Effect of Bariatric Surgery on Metabolic Diseases and Underlying Mechanisms

## TL;DR

Bariatric surgery helps reduce obesity and related diseases like diabetes and fatty liver by altering digestion and hormone levels, though it can cause some nutritional deficiencies.

## Contribution

This review summarizes the mechanisms by which bariatric surgery improves metabolic health and highlights associated complications.

## Key findings

- Bariatric surgery reduces body mass index and improves comorbidities like T2DM and NAFLD.
- Hormonal changes, including GLP-1 and PYY, contribute to metabolic improvements after surgery.
- Complications such as osteoporosis and anemia are linked to altered nutrient absorption post-surgery.

## Abstract

Obesity is a highly prevalent public health concern, attributed to multifactorial causes and limited in treatment options. Several comorbidities are closely associated with obesity such as the development of type 2 diabetes mellitus (T2DM), cardiovascular and cerebrovascular diseases, and nonalcoholic fatty liver disease (NAFLD). Bariatric surgery, which can be delivered in multiple forms, has been remarked as an effective treatment to decrease the prevalence of obesity and its associated comorbidities. The different types of bariatric surgery create a variety of new pathways for food to metabolize in the body and truncate the stomach’s caliber. As a result, only a small quantity of food is tolerated, and the body mass index noticeably decreases. This review describes the improvements of obesity and its comorbidities following bariatric surgery and their mechanism of improvement. Additionally, endocrine function improvements after bariatric surgery, which contributes to the patients’ health improvement, are described, including the role of glucagon-like peptide-1 (GLP-1), fibroblast growth factors 19 and 21 (FGF-19, FGF-21), and pancreatic peptide YY (PYY). Lastly, some of the complications of bariatric surgery, including osteoporosis, iron deficiency/anemia, and diarrhea, as well as their potential mechanisms, are described.