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Brian Mealey, DDS, MS, discusses the effect of bariatric surgery on type 2 diabetes.

Bariatric Surgery Defined

Bariatric surgery on the stomach and/or intestines is designed to help patients who are morbidly obese lose weight. People with a BMI of 40 or greater are eligible for the surgery. People with diabetes or other health problems like heart disease are considered for the surgery with a BMI between 35 and 40.2 Two types of bariatric surgery are performed: adjustable gastric banding and gastric bypass. Adjustable gastric banding uses the insertion of a band that limits the size of the opening from the esophagus to the stomach. The size of this opening determines how much food the patient can eat. The surgeon can control the size of the opening by inflating or deflating the band through an implantable port located on the abdomen underneath the skin. The band is removable.2 Gastric bypass surgery is a permanent reduction in the size of the stomach. A part of the stomach is used to create an eggsized pouch—which bypasses about 2 feet of the normal intestine—that is linked directly to the intestine. The size of the pouch and the size of the opening between the pouch and the intestine limit the amount of food that can be consumed. The bypassing of part of the intestine is what affects the hormones in the stomach.2

Q. What is the effect of bariatric surgery on people with type 2 diabetes?

A. When performed on obese or morbidly obese patients with type 2 diabetes, the research shows that bariatric surgery completely resolves approximately 75% of this patient population’s diabetes.1 Most of these patients essentially do not have diabetes any longer, following the surgery. (See sidebar for more information on bariatric surgery.2)


Q. Are these results unrelated to weight loss?

A. No, essentially, the number one risk factor for type 2 diabetes is being overweight. As a nation, the fatter we get, the greater the incidence of type 2 diabetes. Obesity, especially morbid obesity, dramatically increases the risk of type 2 diabetes. Overweight and obese are defined by body mass index (BMI), a number calculated from a person’s weight and height. Table 1 provides an example of BMI for a person who is 5’9”. An adult who has a BMI between 25 and 29.9 is considered overweight and an adult with a BMI of 30 or higher is considered obese.3 Those with a BMI greater than 35 are considered morbidly obese.4 Addressing a weight problem in people with type 2 diabetes can also have a profound effect on their diabetes without bariatric surgery. If 10% of their body weight is reduced, their need for medication may be eliminated or greatly reduced. Cytokines produced by fat cells increase insulin resistance. In order for glucose to be used by muscle cells properly, insulin needs to allow the glucose to get out of the bloodstream and into the muscle cells. In people without diabetes, when they eat a meal and their blood sugar level rises because there was glucose in the meal (carbohydrates), their blood glucose level rises. In order for the glucose to get out of the bloodstream and into the muscle where it’s used for energy, the body has to be producing insulin and the insulin has to be able to bind to the receptors that are on the muscle cells. People with type 2 diabetes develop insulin resistance. Their pancreas is making insulin but when it goes out in the bloodstream and into the receptors on the muscle cell, it doesn’t work properly. Because the insulin doesn’t work on the muscle cell that means the door of the muscle cell will not open. It won’t allow glucose to get inside the muscle cell.

Table 1: Example of body mass index for a person who is 5’9″.3
Weight Range
124 lbs or less
Below 18.5
125 lbs to 168 lbs
18.5 to 24.9
Healthy weight
169 lbs to 202 lbs
25.0 to 29.9
203 lbs or more
30 or higher


Q. What about the people who are seeing a remission of their diabetes almost immediately following the bariatric surgery before there is time for significant weight loss?

A. The surgery creates a short-term effect and a long-term effect. The main long-term effect is that the patient loses weight. When weight is lost, the insulin sensitivity is restored to normal.

Diabetes is often resolved days after the bariatric surgery before significant weight is lost. This resolution is due to hormonal factors. The hormones in the stomach that mediate the way that glucose is metabolized are affected differently when the distal stomach is bypassed. The study of the impact of various bariatric procedures on gut hormones is receiving increasing attention. When the stomach is bypassed, there is a host of hormones that are produced in the gastrointestinal tract that affect glucose metabolism. Many of these are produced in the stomach. If the stomach is bypassed, many of those hormones are no longer produced. Some of those hormones adversely affect glucose metabolism. When these hormones are eliminated, glucose metabolism is restored to normal even without weight loss. Current metabolic studies of patients with diabetes who are undergoing bariatric surgery have shown improved insulin dynamics, a decrease in inflammatory mediators, and an improvement in insulin sensitivity.1 In other words, hormones in the gut can adversely affect insulin sensitivity, making the tissues more resistant to insulin and when the stomach is bypassed, the elimination of the hormones from the system improve insulin sensitivity.

Q. Does bariatric surgery have any effect on people with type 1 diabetes?

A. People with type 1 diabetes are almost never obese. A normal hormone level does not adversely affect insulin levels. In obesity, there is an increase in the production of those hormones that are bad for glucose metabolism. So bypassing the stomach in thin people with type 1 diabetes won’t have any effect. Bypassing the obese person’s stomach will. Bariatric surgery is not a solution for the majority of people with diabetes but it may become the treatment of choice for people with type 2 diabetes who are obese or morbidly obese. Currently, there is a lot of debate over whether Medicare should cover bariatric surgery for people with type 2 diabetes. Bariatric surgery is still considered elective. As the benefits of bariatric surgery in obese patients with type 2 diabetes become more clear, chances are that insurance programs will begin to cover the procedure.


  1. Dixon JB, O’Brien PE, Playfair J, et al. Adjustable gastric banding and conventional therapy for type 2 diabetes: a randomized controlled trial. JAMA. 2008;299:316-323.
  2. Definition of bariatric surgery. Available at: Accessed April 29, 2008.
  3. Defining Overweight and Obesity. Available at: Accessed April 29, 2008.
  4. Tessaro I, Mangone C, Parkar I, Pawar V. Knowledge, barriers, and predictors of colorectal cancer screening in an Appalachian church population. Prev Chronic Dis. 2006;3:A123.

From Dimensions of Dental Hygiene. September 2008; 6(9):24, 26.

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