Guest post by Matt Papa
Of the nearly 24 million Americans that have diabetes, the majority are type 2, a disorder where the body is unable to properly use or make enough insulin [1]. If left untreated, type 2 diabetes can lead to severe and even life-threatening complications including heart disease, stroke, high blood pressure, blindness, kidney disease and amputation. While there are several risk factors associated with developing type 2 diabetes, research shows that 90% of all people with this particular type of diabetes are either overweight or obese [2].
A recent meta-analysis published in the March 2009 issue The American Journal of Medicine examined the results from more than 620 studies involving one form or another of bariatric surgery. The analysis found that bariatric surgery is an overall powerful treatment option in helping to improve or even resolve the clinical manifestations associated with type 2 diabetes in obese people.
Differences Between the Types of Bariatric Surgery
Currently, there are several types of bariatric surgery that are typically performed on obese patients. Laparoscopic adjustable gastric banding, gastric bypass and biliopancreatic diversion/duodenal switch procedures are the most commonly performed types of bariatric surgery. These procedures are usually performed on those who have been defined as morbidly obese, which is having a body mass index (BMI) of more than 40 kg/m2 or more than 35 kg/m2 with the presence of obesity-related comorbidities [3].
In laparoscopic adjustable gastric banding surgery, an inflatable tube is placed around the stomach to limit food intake. The diameter of the tube, which determines the degree of stomach restriction, can be adjusted by the addition or removal of saline through a tube that is placed right beneath the abdominal wall. In gastric bypass surgery, a portion of the stomach is removed and reconnected to a lower part of the small intestine. The restrictive and malabsorptive nature of gastric bypass results in a smaller stomach and less overall food absorption within the small intestine. Finally, the biliopancreatic diversion/duoduenal switch procedure is very similar to the gastric bypass surgery, except for the fact that a larger portion of the small intestine is bypassed resulting in a greater malabsobsorption.
Two Meta-Analyses Reach Similar Conclusions
A previous meta-analysis of 134 studies conducted in 2004 and published in the Journal of the American Medical Association had similar results to a larger, more recent meta-analysis. In the earlier study, the use of bariatric surgery was found to resolve type 2 diabetes in patients who underwent either laparoscopic adjustable gastric banding, gastric bypass or biliopancreatic diversion/duodenal switch procedures in 48%, 84% and 98% of patients, respectively [4].
The purpose of the second analysis was to further explore these earlier findings and update the meta-analysis to include additional studies conducted since 2004. As such, the second meta-analysis study was designed to evaluate all studies on gastric banding, gastroplasty, gastric bypass, and biliopancreatic diversion/duodenal switch procedures published between January 1, 1990 and April 30, 2006. The analysis examined weight loss and resolution of diabetes by procedure in the total patient population as well as in those with diabetes alone.
A total of 621 studies with 125,246 patients were included in the second meta-analysis. The average age of those included in the studies was 40.2 years, which ranged from the youngest patient at 16 years old to the oldest patient at 65 years old. The majority of the patients were female (80%) and approximately 10.5% had undergone previous bariatric surgeries. Furthermore, the average body mass index (BMI) of the patients was 47.9 kg/m2, which is defined as morbidly obese, and 22.3% had type 2 diabetes.
Which Bariatric Procedure Was More Effective For Weight Loss And Diabetes Resolution?
In the total study population, greater weight loss was seen in those undergoing the biliopancreatic diversion/duodenal switch procedure followed by the gastric bypass, gastroplasty and laparoscopic adjustable gastric banding, respectively. Total excess weight loss was found to be 53.8% at less than two years after surgery and 59% after two years or more of follow-up post-operatively. In the study population that had type 2 diabetes at the start of each study, the total excess weight loss was 67.1% at less than two years following surgery and 58% after two years or more following surgery.
In all of the 621 studies included in the analysis, 86.6% of patients had their diabetes improved or resolved following bariatric surgery. Of these patients, 78.1% had complete resolution of their type 2 diabetes. Resolution was greatest in those that underwent a biliopancreatic diversion/duodenal switch procedure (95.1 %), followed by the gastric bypass (80.3 %), gastroplasty (79.7 %) and laparoscopic adjustable banding (56.7 %) procedures. Resolution of diabetes was associated with significant decreases in insulin levels, hemoglobin HgA1c concentration (a form of hemoglobin that is used to measure levels of blood glucose over the course of time) and fasting blood glucose levels following surgery.
Weight and Diabetes: A Total Cause and Effect?
While this study clearly demonstrates that weight loss following bariatric surgery can both improve and resolve the symptoms associated with type 2 diabetes, there is strong evidence that the relationship between excess weight and diabetes is not that of cause and effect. In fact, an observation made in other studies is that type 2 diabetes was totally resolved in some patients within days after the bariatric surgery, before there was any significant weight loss [5,6,7]. This finding suggests that weight loss is not the only factor responsible for the resolution of type 2 diabetes. It appears that the hormonal and biochemical alterations in the gastrointestinal system brought about by bypass surgery influence directly the development of type 2 diabetes.
The results presented in this meta-analysis demonstrated the powerful effect of bariatric surgery in treating type 2 diabetes. The authors of the study conclude that randomized clinical trials that compare bariatric surgery to medical therapy are necessary to complete in order to determine which course of treatment is best for reducing the complications associated with type 2 diabetes in morbidly obese patients.
Matt Papa, Ph.D. has a special interest in the field of obesity treatment. Obesity is recognized as a major risk factor for cardiovascular disease – Matt’s research field for the past eight years. In his web site, Matt presents the latest scientific research on a variety of weight loss-related topics, writes reviews about weight loss diets and offers a savings coupon for Medifast, a doctor-recommended diet.
References
1. Centers for Disease Control and Prevention. National diabetes fact sheet: general information and national estimates on diabetes in the United States, 2007. Atlanta, GA: US Department of Health and Human Services, Centers for Disease Control and Prevention, 2008.
2. Mokdad, A, Bowman, B, Ford E, et al. The continuing epidemics of obesity and diabetes in the United States. JAMA. 2001;286:1195-1200.
3. National Institutes of Health Consensus Development Panel. Gastrointestinal surgery for severe obesity. Ann Intern Med. 1991;115:956-961.
4. Buckwald H, Avidor Y, Braunwald E, et al. Bariatric surgery: a systematic review and meta-analysis. JAMA. 2004;292:1724-1737.
5. Pories W, Swanson M, MacDonald K, et al. Who would have thought of it ? An operation proves to be the most effective therapy for adult-onset diabetes mellitus. Ann Surg. 1995;222:339-352.
6. Pories W, Albrecht R. Etiology of type II diabetes mellitus: role of the foregut. World J Surg. 2001;25:527-531.
7. Hickey M, Pories W, MacDonald K, Jr., et al. A new paradigm for type 2 diabetes mellitus: could it be a disease of the foregut? Ann Surg. 1998;227:637-643.
