Introduction
A condition where abnormal or excessive fat accumulation occurs in the adipose tissue to the point where health is compromised is known as obesity. This is regarded as a risk factor for several chronic illnesses, such as colon cancer, hypertension, type 2 diabetes, nonalcoholic fatty liver disease, and cardiovascular diseases. It is a considerable health burden in society, and it has been linked to an increase in mortality rates. Currently, Bariatric Surgery (BS) is the only long-term effective therapeutic option for patients with severe obesity.
What Is Bariatric Surgery?
The introduction of bariatric surgery as a weight loss method has been quickly adopted as the most efficient method of weight loss and blood sugar level reduction. Bariatric surgery, also known as weight loss surgery, is a type of surgical procedure used to help people who are obese lose weight. If other weight loss methods have failed and obesity appears to pose a greater risk to health than surgery, healthcare providers may recommend bariatric surgery. Bariatric surgery treatments work by changing the digestive system, mostly the stomach, but sometimes the small intestine is also altered. This is done to limit the number of calories consumed and absorbed. The procedure can also suppress hunger signals sent from the digestive system to the brain. While bariatric surgery can help treat obesity, there is a chance of certain side effects, like internal herniation (internal organs protruding from the abdominal walls), slippage, erosion of the mesh, gastroesophageal reflux (a condition where the acidic contents from the stomach come back to the esophagus), nutritional deficiencies, and marginal ulcerations.
What Are the Various Bariatric Surgeries Available?
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Roux-en-Y Gastric Bypass (RYGB): This is the gold standard and most widely used bariatric surgery globally. The procedure is divided into two steps. The capacity of the upper stomach is reduced to the size of an egg in the first stage. This is then directly attached to a part of the small intestine called the ‘Roux limb’. As a result, the food consumed bypasses the rest of the stomach and the first part of the intestine. This reduces the amount of nutrients the body absorbs, leading to weight loss.
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Laparoscopic Sleeve Gastrectomy (LSG): In this procedure, the remaining eighty percent of the lateral part of the stomach is removed, leaving behind a long tubular gastric tube. This is usually considered in highly obese people whose body mass index (BMI) is more than 50 kg/m². The nutrient intake is reduced as the gastric volume is reduced.
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Laparoscopic Adjustable Gastric Banding (LAGB): This procedure keeps adjustable silicone bands in the upper parts of the stomach. This forms a small gastric space over the band. By injecting sterile saline through the abdominal wall, the gap between the upper stomach space and the back of the stomach can be made smaller or larger. The band can be gradually adjusted over time during postoperative follow-up.
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Biliopancreatic Diversion (BPD): This procedure has three parts;
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The distal ileoanal anastomosis,
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The proximal duodenal bile duct anastomosis,
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Tube stomach with the pylorus retained.
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The reduced stomach capacity, Ghrelin hormone levels, and an increase in peptide YY (a hormone in the small intestine) contribute to weight loss.
What Is Gut Microbiota?
The microbiota is a community of microorganisms found in a prominent biological area or location. The human body is believed to have over 1,014 microorganisms, more than seventy percent of which are in the colon, and more than 35,000 bacterial strains are in the gastrointestinal system. It has been asserted that the human gut microbiota comprises about 1,000 different species. In healthy people, it can be divided into six bacterial groupings. Firmicutes, Bacteroidetes, Proteobacteria, Actinobacteria, Fusobacteria, and Verrucomicrobia are among them. Changes in microbial content have a substantial impact on human health. Many non-communicable diseases, like obesity, type 2 diabetes, asthma, allergies, atopic diseases, inflammatory bowel disease, metabolic syndrome, necrotizing enterocolitis, and atherosclerosis, have been linked to the intestinal microbiota.
How Is Gut Microbiota Altered After Bariatric Surgery?
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Dietary Changes: Following bariatric surgery, Significant gut flora alterations have been reported. Food choices and preferences, reduced food consumption, and nutrient malabsorption are all potential reasons for alterations in the gut flora. Short-term dietary changes can produce dramatic changes in the gut microbiota composition. Prevotella enterotypes have been linked to both complex carbohydrate-rich and simple carbohydrate-rich diets. In contrast, Bacteroides enterotypes have been linked to a typical ‘Western diet’ high in animal protein and saturated fat. Low-fat, high-carbohydrate diets, and high-carbohydrate, low-glycemic-index diets, in particular, alter the quantities of distinct strains in the gut microbiota differently. Diet therapy after bariatric surgery alters microbiota for the same reasons.
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Role of Bile Acids: Bile acids have been reported to be a second factor influencing the shift in microbiota following bariatric surgery. They can self-regulate their synthesis and intestinal reabsorption by modulating the nuclear-located farnesoid X receptor (FXR). Recently, a connection has been established between the physiological function of beta-cells, glucose homeostasis, energy consumption, and the involvement of bile acids. In RYGB, biliopancreatic extract, biliary fluid, and nutrients are isolated. Nutrients and bile acids combine in the lower sections of the intestine. The proximal ileum and distal jejunum receive an excessive amount of nutritional exposure. The bile acids cover dietary lipids, while the bile acid cycle in the upper stomach gets reduced. The benefit of bariatric surgery is due to the changes in the metabolism of bile acids.
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Hormones and pH: Hormones like ghrelin and leptin can fluctuate following bariatric surgery. This can also alter the microbiota and energy metabolism. It has been shown that pH (potential of hydrogen) variations are another factor influencing microbiota. As the stomach's volume decreases following surgery, pH rises. Microbiota can be significantly impacted by elevated pH.
Conclusion
Bariatric surgery is an effective treatment option for obesity. It is quite successful at achieving and maintaining weight loss. The success following a bariatric surgery is not just linked to food consumption. The changed microbiota following bariatric surgery also affects its efficacy. Malabsorption after bariatric surgery, changes in bile acid metabolism, changes in stomach pH, and changes in hormone metabolism all lead to changes in the gut microbiota. Changes in microbiota also have an impact on energy homeostasis.
