Impact of Bariatric Surgery on Diabetes

By Matthew Constantin, PhD

The correlation between weight and diabetes has long been commonly recognized throughout society.  More recently, a clinical research study conducted by a team of professionals headed by Dr. Henry Buchwald, set out to analyze the impact of bariatric surgery procedures on Type 2 Diabetes [1].  Published in The American Journal of Medicine, the findings systematically reviewed the restrictive procedures known as adjustable lap banding and permanent stomach stapling, and a combination of restrictive and malabsorptive procedures known as gastric bypass and biliopancreatic diversion with duodenal switch.  The objective was to determine outcomes on diabetes associated with the type of bariatric procedure and subsequent weight loss results. Study results indicated that diabetes was reduced or resolved in the majority of bariatric surgery patients.  Interestingly, the surgical intervention causing the greatest reduction of weight combined with a maintenance period of at least 2 years, also achieved the highest percentage of diabetes resolution.

The Weight Loss Surgery-Diabetes Study

The team collected studies published from January 1990 through April 2006 by conducting a MEDLINE electronic search.  Data from 135,246 patients in 621 studies was accessed. Patients ranged in age from 16 to 65 years with a mean age of 40.2 and BMI of 47.9. Females made up about 80% of the group, while patients with type 2 diabetes accounted for 22.3% of cases.

The procedures analyzed involved banding, gastroplasty, gastric bypass and duodenal switch.  Results stayed consistent for a minimum of two years.  Study findings were determined by laboratory parameters of HbA1c, glucose and serum insulin.  HbA1c is a form of hemoglobin the levels of which provide a good indication of glucose concentration in the blood over time.

What Were The Research Results?

Of clinical significance, the Buchwald research study indicated:

• Type 2 diabetes was resolved in 78% and resolved or improved in 87% of patients undergoing bariatric surgery.
• There was a progressive relationship of diabetes resolution and weight loss achieved as a function of the operation performed: laparoscopic adjustable gastric banding, gastroplasty, gastric bypass, and biliopancreatic diversion/duodenal switch.
• Clinical findings were substantiated by the laboratory parameters of serum insulin, HbA1c and glucose.
• These findings were maintained for 2 years or more.

Weight Loss Results For All Participants

Biliopancreatic diversion/duodenal switch patients achieved the most weight loss.  The most common procedure, gastric bypass, accounted for the second best weight loss total.  Body weight for gastroplasty was next followed by laparoscopic adjustable gastric banding. Weight loss for at least half of all groups equaled 59% of excess body weight at 2 or more years following surgery. Weight loss for at least half of the diabetic patients for the same time period rated over 67% of excess body weight.

Results  for Diabetics

The pattern reoccurred for diabetes regarding effectiveness of the type of procedure.  Specifically, for duodenal switch surgeries over 95% of patient diabetes was resolved.  Gastric bypass patients who no longer had the disease was next at over 80%.  Slightly lower, gastroplasty cleared the disease in over 79% of diabetics and the lap band procedure eliminated the diabetes for over 56% of patients.  Diabetic patients undergoing bariatric procedures noted a 78.1% resolution overall.

Following surgery, HgA1c dropped significantly along with lower insulin levels and fasting glucose values. That means that diabetes was improved.

Some Important Points To Consider

Weight is the main risk factor for patients with type 2 diabetes as over 90% are ranked as overweight or obese [2]. During the past 10 years type 2 diabetes has increased dramatically throughout the world [3]. During the same time period the portion of the population rated as obese also climbed at an alarming rate [4].

The National Institute of Health places a BMI of 40 as morbid obese.  In the case of related disease that could lead to death due to weight, morbid obesity is defined as a BMI of 35 [5]. In the United States over 8 million people have a BMI of 40 or more and approximately 23 million record a BMI of 35 or more [6].

Through documented serum insulin levels (HgA1c and fasting blood glucose), this clinical research study shows that bariatric surgery can eliminate type 2 diabetes.  In addition, other clinical studies have indicated surgical intervention through bariatric procedures benefits patients by living longer and have fewer problems with other diseases [7].

Weight and Diabetes: Cause and Effect?

Evidence suggests that excess weight and diabetes are not in direct cause-and-effect relationship. In other words, it is still not known whether excess weight is the cause of diabetes or the result of it. If weight is the cause of diabetes then the disease should resolve only after significant post-surgery weight loss has occurred. In reality, though, prior to any significant weight loss, within a few days after surgery many patients are totally clear from their diabetes symptoms.  Therefore, the cause and effect related to weight and diabetes is not direct. This leads researchers to the conclusion that other chemical changes within the body influence type 2 diabetes [8].

Conclusion

Morbidly obese diabetic patients experience a powerful benefit after undergoing bariatric surgery.  Diabetes was erased in approximately 80% of patients within 2 years while 62% remained free of the disease after surgery for longer than 2 years.

About the author: Matthew Constantin

A biologist and research fellow at Washington University School of Medicine in St. Louis MO, Matthew Constantin, PhD, studies scientific reports from peer-reviewed medical journals summarizing the latest findings concerning optimal weight loss methods. His interest in the topic of weight loss, nutrition and diet has lead him to establish a website, where he offers promotion discount coupons for Nutrisystem and a coupon code for Diet To Go, two popular online weight loss programs.

References

1. Henry Buchwald, MD and associates, Weight and Type 2 Diabetes after Bariatric Surgery: Systematic Review and Meta-analysis, The American Journal of Medicine,  2009; 122: 248-256.

2. AH Mokdad and others, The continuing epidemics of obesity and diabetes in the U.S. The American Journal  of Medicine, 2001; 286: 1195-1200.

3. AH Mokdad and others, Diabetes trends in the U.S. Diabetes Care, 2000; 23: 1278-1283.

4. S Wild and others, Global prevalence of diabetes, Diabetes Care, 2004; 27: 1047 1053.

5. National Institutes of Health Consensus Development Panel, Gastro-intestinal surgery for severe obesity.  Ann Intern Med. 1991; 115: 956-961.

6. CDC/NHANES, Overweight and obesity: Obesity trends: US Obesity Trends 1985-2005. 7. Available at: http://www.cdc.gov/nccdphp/dnpa/obesity/trend/ maps/indes.htm, Accessed Jun18, 2007.

7. DR Flum, Impact of gastric bypass operation on survival: a population-based analysis, J Am Coll Surg. 2004; 199:543-551.

8. F Rubino and others, The mechanism of diabetes control after gastrointestinal bypass surgery reveals a role of the proximal small intestine in the pathophysiology of type 2 diabetes, Ann Surg.  2006; 244: 741-749.

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