Bariatric Surgery and Diabetes


According to the American Diabetes Association, 30.3 million Americans, or 9.4% of the population, have diabetes. Diabetes remains the 7th leading cause of death in the United States. It is a disease characterized by high levels of blood glucose resulting from defects in insulin production and/or insulin action.

Type 1 diabetes accounts for about 5-10% of all cases. Type 1 diabetes develops when the body’s immune system destroys pancreatic beta cells, the only cells in the body that make the hormone insulin that regulates blood glucose. This form of diabetes usually strikes children and young adults, although disease onset can occur at any age.

Type 2 diabetes accounts for some 90 to 95 percent of all diagnosed cases. It usually begins as insulin resistance, a disorder in which the cells do not use insulin properly. As the need for insulin rises, the pancreas gradually loses its ability to produce it. The risk of type 2 diabetes is 3-7 times higher in those who are affected by obesity than in normal-weight adults, and is 20 times more likely in those with a body mass index (BMI) greater than 35kg/m 2. In this article, we will discuss the role of obesity in diabetes, as well as the different treatment options, focusing on the how bariatric surgery affects diabetes.

Weight loss is an important goal for persons affected by excess weight or obesity, particularly those with type 2 diabetes. Moderate and sustained weight-loss (5-10 percent of body weight) can improve insulin action, decrease fasting glucose concentrations and reduce the need for some diabetes medications. A program of diet, exercise and behavior modification can, on some occasions, successfully treat obesity; but pharmacotherapy and/or surgery is usually warranted.

For the patient affected by obesity with diabetes or insulin resistance, limiting servings of complex carbohydrates may be beneficial. These foods include bread, rice, pasta, potatoes, cereal, peas and sweet potatoes. Complex carbs tend to raise blood sugar more than other foods and will cause the body to produce more insulin. With insulin resistance, these increased amounts of insulin can promote weight gain.

Bariatric surgery has the amazing ability to prevent and treat diabetes. It does so through a complex mechanism affecting all parts of the digestive system.

Increasing the amount of fiber in the diet may also be beneficial for both diabetes and obesity. A high intake of dietary fiber, particularly of the soluble type, may improve glycemic control, decrease hyperinsulinemia and lower plasma lipid concentrations in patients with type 2 diabetes. Additionally, high fiber foods assist in weight-loss and long-term weight maintenance by requiring more chewing and taking longer to eat, providing fewer calories per serving, creating a sense of abdominal fullness and enhancing fullness between meals.

Regular physical activity helps maintain weight loss and prevents regain. It also improves insulin sensitivity and glycemic control, and may decrease the risk of developing diabetes. A goal should be set for 30-45 minutes of moderate exercise five times per week. The exercise does not need to occur in a single session to be beneficial. Dividing the activity into multiple and short episodes produces similar benefits and can enhance compliance. Using a smart phone/watch can help set objective exercise goals. Any increase in activity over baseline will help in balancing the equation of less calories in and more calories out to promote weight-loss.

There are several medications intended to treat diabetes, insulin resistance and obesity. A full review of these medications is beyond the scope of this article. However, metformin is one of the most commonly prescribed medications that has been found helpful in reducing the risk of type 2 diabetes in people with insulin resistance. Metformin reduced the rate of progression to diabetes in persons affected by obesity with impaired glucose tolerance.

According to the National Institute of Health (NIH), bariatric surgery should be considered by those who have a BMI greater than 40, or have a BMI of 35-39.9 and medical problems such as diabetes, heart disease or sleep apnea. Bariatric surgery changes the normal digestive process. Studies continue to show that diabetes can be cured in many patients using bariatric surgery. These clinical improvements occur not only because of the significant weight loss, but because of hormonal changes that occur when foods bypass the stomach. This is why the surgery is also called metabolic surgery. Patients and their doctors need to consider the possible risks of bariatric surgery compared to the ongoing and progressive risk of obesity and the associated medical problems. When other methods of weight loss have failed, bariatric surgery may be the best chance for significant and sustained weight loss and diabetes resolution.

Bariatric surgery achieves resolution of diabetes in a very complex and intertwined manner that is continuing to be understood. What we have learned is that there are several mechanisms that come into play.

Decreased Calorie Intake

After bariatric surgery, an individual usually consumes about 700-1,000 calories per day. This is less than their metabolic rate, which produces rapid weight loss and assists with diabetes resolution. Reducing caloric intake helps to begin the process of reversing insulin resistance. With weight loss, the liver and skeletal muscle cells lose fat from inside the cell which makes them more sensitive to insulin.

However, weight loss takes time, and for over 50 years, bariatric surgeons have noticed that their patients’ diabetes often resolves immediately after surgery – before the patient has had any significant weight loss. So, this implies other mechanisms may play greater roles, and so, we will look at each of the intestinal areas affected by bariatric surgery.


The stomach produces hormones that are involved in glucose regulation, such as ghrelin, gastrin and glucose-dependent insulinotropic polypeptide (GIP). Bariatric surgery alters the size of the stomach, changing the secretion of these hormones.

Ghrelin is made primarily in the top part of the stomach. It is the only known appetite-stimulating hormone in the body, and it also acts to reduce insulin secretion after a meal. After bariatric surgeries such as sleeve gastrectomy and gastric bypass, ghrelin levels drop up to 75 percent – causing patients to have a reduced appetite, secrete more insulin and have lower blood sugar levels.

Likewise, gastrin is produced in the lower part of the stomach (also by the small intestine and pancreas) after eating. Gastrin makes us feel full by stimulating the pancreas to make more insulin after we eat a meal. This also has the effect of improving diabetes. Gastrin production is increased after surgery.

After gastric bypass, glucose-dependent insulinotropic polypeptide (GIP) levels are elevated and cause the pancreas to release more insulin. This causes the liver and muscle cells to remove glucose from the bloodstream and produce lower blood sugar levels.

Small Intestine

Bariatric surgery also affects how food interacts with the small intestine. Bypassing or speeding the transit of food through the first part of the small intestine improves diabetes because specialized endocrine cells secrete anti-diabetic compounds in the absence of food. While there are over 15 recognized endocrine changes, the most described and studied are GLP-1 (Glucagon-like peptide-1), OXM (Oxyntomodulin) and PYY. After bariatric surgery, GLP 1 is elevated, causing the pancreas to secrete more insulin. This has been shown to help the pancreas cells which make insulin (beta cells) revive after damage from diabetes. OXM improves diabetes by causing intestinal cells to remove sugar from the bloodstream, causing people to burn more energy through improved metabolism and reduced appetite due to satiety. PYY appears to improve diabetes by stimulating the brain to release a hormone called alpha MSH that decreases appetite. PYY is elevated after bariatric surgery.

Lower Intestine

In the large intestine, also called the colon, live all the bacteria responsible for breaking down and actually absorbing all of the nutrients and calories in food. We have a harmonious relationship with the bacteria in our colon. Studies have shown that in people who develop morbid obesity, the types of bacteria in the colon change and become a considerable cause for the persistence of obesity. Research into the types of bacteria found and the affect of bariatric surgery has revealed that the surgery causes a change in the bacteria that results in a more normal state. This change in bacteria back to pre-obesity levels is believed to play a major role in weight loss and diabetes control. A tremendous amount of research is ongoing in developing methods to alter the bacteria in obese people with type 2 diabetes as a potential long-term nonsurgical treatment option for weight loss and diabetes control.

In summary, bariatric surgery has the amazing ability to prevent and treat diabetes. It does so through a complex mechanism affecting all parts of the digestive system. The anti-diabetic effects are proven to be more effective than the best medicines available. As effective as bariatric surgery is, we know that the real treatment for our obesity epidemic is prevention. Promoting a healthy lifestyle in children and adolescents will put them on a path that will decrease their risk of diabetes and its complications. Helping adults at high risk for diabetes to change their diet and lifestyle may prevent them from developing diabetes and its consequences.



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