September 2010 Issue
Bariatric Surgery for Type 2 Diabetes
By Joyce Green Pastors, RD, MS, CDE
Today’s Dietitian
Vol. 12 No. 9 P. 44
Suggested CDR Learning Codes: 5190, 5370, 5410; Level 2
In recent years, because of the strong connection between type 2 diabetes and obesity, widespread media reports have suggested that weight loss can cure diabetes. In extreme cases, people have even undergone bariatric surgery.
Bariatric surgery (or weight-loss surgery to many laypeople) refers to one of several surgical procedures used to treat unresolved obesity. The surgery’s popularity has increased in recent years: In 2002, 90,000 adults in the United States had bariatric surgery; in 2004, surgeons performed more than 140,000 procedures; and an estimated 205,000 individuals had bariatric surgery in 2007.1
For many individuals who are severely obese, especially patients with diabetes who have not controlled their weight, surgery seems promising—a quick fix. But the question remains: Can surgery truly reverse diabetes? This article will address that question and help dietitians understand the complex relationship between diabetes and obesity and the effects of weight-loss surgery.
The American Diabetes Association states that “gastric reduction surgery can be an effective weight-loss surgery for obesity and may be considered in people with diabetes who have a body mass index (BMI) [of or greater than] 35 kg/m2.” This figure defines severe obesity, according to National Institutes of Health guidelines established in 1992, and bariatric surgery is presently only available as a treatment for severe obesity as defined in the guidelines.
A 2007 Diabetes Surgery Summit meeting to agree on a set of evidence-based guidelines and definitions sought to guide the use and study of gastrointestinal surgery to treat type 2 diabetes. The summit’s consensus statement describes the BMI cutoff of 35 kg/m2 as arbitrary and unsupported by scientific evidence, noting that “surgery should be considered for the treatment of type 2 diabetes in patients with a BMI of 35 or more who are inadequately controlled by lifestyle and medical therapy, but may also be appropriate for people with type 2 diabetes and merely mild-to-moderate obesity (BMI of 30-35).”
The possibility of a surgical intervention was thus held out to millions of people with diabetes who were less than severely obese. But, of course, there is no quick fix, and surgical intervention has limits and risks. To understand them better, let’s discuss bariatric surgery itself.
Bariatric Surgery Defined
Weight-loss, bariatric, and gastric-reduction surgery all reduce the size of the stomach to limit the amount of food a person can eat, thereby changing the digestive system. Each type of bariatric surgery has benefits and risks, and each impacts health, eating behavior, and nutritional status in some way.
Types of Procedures
The two major types of bariatric surgery for patients who are obese are gastric bypass surgery and gastric restriction surgery, each having different effects on gut hormone secretion and thus on insulin secretion and sensitivity. The choice of procedure should involve BMI, age, gender, and comorbidity considerations.
Gastric Bypass Surgery
Gastric bypass surgery is indicated for people who are unable to achieve or maintain a healthy weight through diet and exercise, who are severely overweight, and who have health problems as a result. It is an option if the individual meets the following criteria:
• BMI of 40 or higher (extreme obesity) or BMI of 35 to 39.9 (obesity) and two comorbidities (eg, diabetes, hypertension, cardiac disease, hyperlipidemia, sleep apnea, arthritis);
• multiple “failures” with nonsurgical weight-loss methods;
• acceptable risk for surgery;
• no evidence of alcohol or drug abuse;
• psychological readiness;
• free of disordered eating patterns; and
• supportive family members.
Gastric bypass surgery doesn’t replace the need to eat healthfully and exercise. The surgery’s success depends on an individual’s commitment to incorporate a plan of healthful eating and physical activity.2,3 The following are the types of gastric bypass surgery:
Roux-en-Y Gastric Bypass (RYGB)
This is the preferred method of gastric bypass surgery and is often considered the gold standard of weight-reduction surgery. The goal of RYGB surgery is to reduce the size of the stomach and to bypass the duodenum and proximal jejunum. The effect is to physically limit the volume and rate of food intake as well as the absorptive capacity of the small intestine. This is accomplished by reducing the stomach to a small pouch (usually 20 mL or less in size) and creating a narrow (10-mm or 0.4-inch) opening, known as a gastrojejunostomy. The distal (lower) end of the jejunum is attached just below the gastrojejunostomy, and the remainder of the original stomach is bypassed.4 The surgery creates a Y-shaped small intestine.
These changes in anatomy substantially impact food and nutrient intake. RYGB is known as a malabsorptive/restrictive procedure.4
Compared with other types of procedures, RYGB offers both clear advantages and disadvantages. One reason for its popularity is that RYGB results in substantial weight loss and significantly greater weight loss than laparoscopic adjustable gastric banding (LAGB). This weight loss results in the rapid reduction, and often complete resolution, of comorbidities such as type 2 diabetes and hypertension. However, RYGB is associated with more side effects and more fatalities than the gastric restrictive procedures. About 10% of patients have postoperative complications.
Deep vein thrombosis/pulmonary embolism, gastrointestinal leakage and bleeding, and infections are some complications that can arise early in the postoperative period. Hernia at the point of incision, ulcers due to an excessive production of gastric acid, small-bowel obstruction, and nutrient deficiencies may arise later. Each patient must consider the risk-to-benefit ratio of RYGB.5
Biliopancreatic Diversion Surgery (BPD)
The goal of BPD surgery, as the name implies, is to divert the bile and pancreatic juices from their original source of introduction to a point much later in the digestive process. It is a more complicated surgery than RYGB and is often used to correct RYGB surgery that has failed to produce significant weight loss.6 Although there is more than one surgical technique, BPD surgery requires partial gastrectomy and the complete bypass of the duodenum and jejunum.
At present, at least two BPD techniques have been reported in the medical literature. One technique, referred to as BPD-distal gastrectomy, involves the creation of a stomach pouch and a distal gastrectomy. Another procedure, known as the duodenal switch or BPD-duodenal switch (BPD-DS), also removes part of the stomach but leaves more of the original stomach intact.
As with RYGB, patients must weigh the risks and benefits of BPD carefully. The advantage of BPD over all other procedures is weight-loss maintenance. There may be some small improvements in comorbidities compared with RYGB. However, the disadvantages are also greater with BPD because of the malnutrition that can occur. Estimates indicate that 2% to 5% of BPD recipients will manifest protein calorie malnutrition. BPD is generally reserved for people who are superobese, especially those with a BMI greater than 60 and those who did not satisfactorily lose weight with RYGB.7
Gastric Restriction Surgery
The rationale behind gastric restriction surgery is to keep the stomach from expanding to accommodate large amounts of food, thus giving the patient an enhanced sense of satiety and making it uncomfortable for him or her to overeat. The following are the common types:
Vertical-Banded Gastroplasty
Often referred to as stomach stapling, this surgery also divides the stomach into two parts, limiting space for food and forcing a patient to eat less. A surgical stapler divides the stomach into upper and lower sections. The upper pouch is small and empties into the lower pouch, or the rest of the stomach. Research has not shown this surgery to result in adequate long-term weight loss, and it isn’t as widely used today as it was in the past.
LAGB
This procedure uses an inflatable band to divide the stomach into two parts by wrapping the band around the upper part of the stomach. The band is pulled tight, creating a tiny channel between the two pouches to restrict the amount of food that the individual can eat. The band keeps the opening from expanding and is designed to stay in place indefinitely. It can be adjusted or surgically removed if necessary. LAGB is a simple procedure and has a lower complication rate than other more involved procedures.
These changes in anatomy impact food intake, dramatically reducing volume. After surgery, patients usually take in less than 1,000 kcal daily, consumed as very small meals throughout the day. In the first three weeks, patients consume only liquids. They typically introduce puréed foods three to four weeks post-op and then eat soft foods for the next two weeks. These guidelines are important because they help prevent band slippage and stretching of the pouch.
In the first months, patients tolerate liquids and soft foods better than any other foods. They generally do not take liquids at the same time as solid foods because liquids quickly fill the pouch. Over time, individuals may progress to solid foods, but many will need soft foods indefinitely. Some foods are not well tolerated (eg, bread, rice, red meat).
Vomiting can be a problem, especially in the first year. Many patients report vomiting once per month, and a small number (estimated at 15%) vomit once per week. Sometimes bloating or other gastric upsets may occur. The majority of postsurgical patients do not report hunger, even though food volume is small and meal frequency is low (usually three meals per day).
There are several advantages to the LAGB procedure. It is minimally invasive, usually requiring five small incisions, and typically takes one hour to perform. The stomach is not permanently altered, so the band can be removed without damaging the stomach. The band can also be adjusted in response to continued weight loss. The greatest advantage is the procedure’s low mortality rate of 0.07%. This makes LAGB the safest of all bariatric surgeries. By comparison, other procedures have a mortality rate of 0.16% to 1.1%.8
But LAGB is not without complications. A disadvantage is that a foreign body may become lodged in the small pouch that was created, resulting in tissue erosion and infections. There are also concerns that the band may slip and partially restrict the esophagus.
LAGB may be the preferred procedure in patients with a history of gastritis and those who use nonsteroidal anti-inflammatory drugs. It may not be as effective in patients with a BMI greater than 50. Proponents of RYGB offer anecdotal evidence that people who seek out a potentially reversible bariatric procedure are not 100% committed to the eating and lifestyle changes that must occur to achieve weight loss.9
Surgery Risks
As with any surgical procedure, gastric surgery involves risks such as bleeding, infection, and reactions to anesthesia. The reported risk of death from bariatric surgery is 0.1% to 2%. Restrictive procedures (eg, LAGB) have lower mortality than malabsorptive ones. Greater risk is associated with increased age (older than 65), gender (male), and poor cardiorespiratory fitness.6
The most common cause of death is pulmonary embolus, but atelectasis (collapsed lungs), peritonitis (due to blood leaking from the pouch or point of attachment of the intestine), and sepsis are possible.
Expected side effects include fatigue, bloating, gastric pain, vomiting, and/or diarrhea, especially in the early weeks following surgery. Most of these conditions will decrease or disappear over time. A wide range of nutritional deficiencies is expected, especially with the surgeries that result in malabsorption. The most serious of these is protein deficiency. Reduced bone mineral content has been reported; whether the risk for osteoporosis increases with bariatric surgery is unknown at this time.
About 12% of all gastric bypass and vertical-banded gastroplasty recipients experience stomal stenosis (narrowing of the opening between the pouch and the small intestine). Symptoms include pain after eating and vomiting. Patients experiencing these symptoms should seek treatment immediately because prolonged vomiting leads to a variety of problems, including dehydration, electrolyte imbalance, thiamin deficiency, and protein malnutrition.2
Professionals should caution potential bariatric candidates about the potential risks, which are highest with BPD. However, these surgeries are also the most successful for reducing and maintaining weight loss and normalizing glucose and lipid metabolism. As with any surgery, the skill of the individual surgeon is a factor in the amount of complications due to surgical technique.
Effectiveness on Weight Loss
While candidates for bariatric surgery must have a BMI of 40 or higher or a BMI of 35 or higher and two comorbidities, surgical success is not based on a defined reduction in BMI. Bariatric surgical “success” is defined as maintaining a weight loss of 50% of excess body weight (EBW) or more for five years. EBW is defined as “total preoperative weight minus ideal weight.” The standard method for reporting is the percentage of EBW lost (weight loss ÷ excess weight x 100). A decrease in BMI of about 10 BMI units is also a realistic measure of bariatric surgical success, but change in BMI is not widely reported in the literature.
A 2004 meta-analysis by Buchwald et al found that the mean percentage of EBW lost in all patients who underwent any kind of bariatric surgery was 61.2%.1 The amount lost was lowest for those who received gastric banding (47.5% EBW lost) and highest for those who received BPD (70.1% EBW lost). The mean percentage of EBW lost for gastric bypass was 61.6%.
These are impressive weight losses, but clearly bariatric surgery is not 100% effective. Also, these are average figures for all surgical patients. Studies have shown that individuals who are superobese have less-favorable outcomes (ie, less weight loss, more weight gain over time).10
For those undergoing RYGB, weight loss typically peaks between 12 and 18 months post-op, when the average amount of weight lost is between 65% and 80% of excess presurgical weight. Weight tends to stabilize at this point and then creep upward for the next 2 1/2 years. Weight gain may be a result of stomach stretching and better absorption as the body adapts to the surgery. By five years post-RYGB, the average excess weight loss is typically between 50% and 60%. In the next 10 years, excess weight loss may vary but generally stays within the 50% to 60% range.11
Cook and Edwards reported the habits of gastric bypass recipients who achieved a weight loss of 50% or more of EBW for five years.12 By surveying patients who had undergone RYGB as early as 1979, the authors identified six habits that were associated with weight-loss maintenance in bariatric surgery recipients and suggested the following guidelines for successful maintenance of weight loss due to gastric bypass surgery:
1. Eating
• Three balanced meals and two snacks daily
• Three servings daily of protein foods
• Three servings daily of vegetables
• One serving daily of fruit
• Two servings daily of bread/starches
• Two servings daily of sweets
2. Drinking
• 40 to 64 oz water daily
• Limit carbonated beverages
• Limit sweetened beverages
• Limit caffeinated beverages
• Limit alcoholic beverages
3. Supplements
• Daily vitamin and mineral supplements
4. Exercise
• Four times per week for at least 40 minutes per session
5. Sleeping
• Average of seven hours per night
6. Personal responsibility
• Personal control of behaviors
• Surgery is a tool, not a panacea
• Weekly scale weight (at home)
• Close self-monitoring of weight (only a few kg of leeway)
Gastric Surgery in Type 2 Diabetes
Increasing evidence demonstrates that bariatric surgery can dramatically ameliorate type 2 diabetes, leading to complete remission of the disease in a large proportion of cases. The 2004 Buchwald meta-analysis of the impact of bariatric surgery on weight loss in patients with four comorbidities (diabetes, hyperlipidemia, hypertension, and obstructive sleep apnea) reviewed 136 studies involving 22,094 patients. The mean percentage of excess weight loss was 61.2% in all patients, and diabetes was completely resolved in 76.8% of patients and resolved or improved in 86%. (The other conditions were similarly improved or resolved.)
Comparing the effects of adjustable gastric banding with conventional therapy for type 2 diabetes, Dixon et al concluded that surgical therapy was more likely to achieve type 2 diabetes remission through greater weight loss.13 Of the 60 patients enrolled (30 in each group) in the study, the surgical group achieved a mean weight loss at two years of 20.7% (BMI from 36.9 to 29.5) compared with 1.7% (37.1 to 36.6) among the conventional therapy group. Also at two years, 80% (n = 24) of the surgical group had hemoglobin A1c (HbA1c) levels less than 6.2% compared with the conventional therapy group at 20% (n = 6).
Looking at long-term follow-up, Schauer et al evaluated the effect of laparoscopic RYGB on type 2 diabetes.14 They compared preoperative and postoperative data, including the duration of diabetes, metabolic parameters, and clinical outcomes over a five-year period. After surgery, weight and BMI decreased from 50.1 (308 lbs) to 35 (211 lbs), a mean weight loss of 97 lbs and excess weight loss of 60%. Fasting plasma glucose levels and HbA1c returned to normal levels in 83% of patients. Patients with the shortest duration (less than five years), the mildest form of type 2 diabetes (diet and exercise controlled), and the greatest weight loss after surgery were most likely to achieve complete resolution of type 2 diabetes.
Given the previous information, bariatric surgery does seem like a magic bullet. But let’s look at the pros and cons of gastric surgery for people with type 2 diabetes.
The Pros
Certainly, the substantial loss of excess weight is the most favorable outcome. The majority of patients in the reported studies lost approximately 60% of their excess weight. Most patients with type 2 diabetes would also agree that resolution of their diabetes or an improvement in glycemic control is equally important. In approximately 80% of the patients with type 2 diabetes, their diabetes resolves, with HbA1c and/or fasting plasma glucose measurements returning to normal. In a narrative review, Vetter et al reported that diabetes resolves after gastric surgery in 84% to 98% of patients with bypass procedures and in 48% to 68% of patients with restrictive procedures.3
Also interesting to discuss are the reasons why glycemic control improves. It is due in large part to caloric restriction and subsequent weight loss but also because of hormonal and metabolic changes. These different gastric surgical procedures have different effects on the enteroinsular axis (connection between the gut and pancreatic islet cells), including effects on hormones called incretins (glucoselike peptide 1 [GLP-1]) and nonincretic gut peptides (peptide YY [PYY] and gherelin). The gastric bypass procedures (RYGB and BPD) increase GLP-1 and PYY levels, but the restrictive procedures do not increase either the incretin or nonincretic gut peptides. These gut peptides increase insulin secretion and improve insulin sensitivity and may mediate a reduction in appetite.3
Patients with type 2 diabetes who undergo gastric surgery also experience a cessation of hypertension and a lowering of cardiovascular disease risk, often to levels below those of normal-weight people in their same age group. In a great majority of patients with type 2 diabetes, the surgery reduces the mortality risks associated with the disease, thereby increasing the quality and longevity of their life, according to information from the Diabetes Surgery Summit.
The Cons
Although gastric surgery appears to resolve diabetes based on HbA1c and fasting plasma glucose measurements in previously reported studies, the postprandial glucose measurement may tell a different story. Roslin et al performed a glucose tolerance test (glucose was measured at one and two hours following a 100-g glucose challenge) in 38 patients approximately six months after gastric bypass surgery. Six of these patients had diagnosed type 2 diabetes prior to surgery. Five of these six patients had normal fasting glucose levels but hyperglycemia (defined as glucose greater than 200 mg/dL) with the glucose tolerance test. HbA1c and fasting blood glucose levels may not be sufficient criteria to determine whether diabetes has been resolved. Measurement of postprandial blood glucose levels and even continuous glucose monitoring may be needed for a more complete objective assessment of glycemic status.15
The marker of excess body weight loss, and even improvements in other markers such as the comorbid conditions noted, should not be the only measures of success in weight-reduction surgery. Economic changes, psychosocial adaptation, and quality of life changes also need to be considered. In most of the research studies looking at the results of gastric bypass surgery, these additional parameters are not even reported, much less evaluated in any systematic way.
Conclusion
Although gastric surgery in people with type 2 diabetes has been shown to ameliorate diabetes or vastly improve glycemic control, it should not be the treatment goal for every overweight or obese person with type 2 diabetes. Surgery is not the only effective treatment for diabetes. Weight loss through lifestyle changes in eating and physical activity have also been demonstrated to be effective.16,17 Although the weight losses in the lifestyle intervention studies are not nearly as dramatic, there are improvements in glycemic control and other clinical parameters associated with diabetes such as high blood pressure and hyperlipidemia.
There is a need to promote, emphasize, and financially support prevention strategies for diabetes, not rely on exotic treatment of its complications. By reimbursing dietitians for medical nutrition therapy and other preventive strategies, insurers can alleviate the need for bariatric surgery in all but the most severe cases. By increasing the number of lifestyle intervention programs available, we can reduce obesity and work to decrease the comorbidities of type 2 diabetes. It is a question of priorities.
— Joyce Green Pastors, RD, MS, CDE, is a diabetes nutrition specialist and assistant professor of education in internal medicine at the University of Virginia School of Medicine in Charlottesville.
Learning Objectives
After completing this continuing education exercise, the student should be able to:
1. Discuss the current guidelines for using bariatric surgery for people who are obese and have type 2 diabetes.
2. Identify the types of bariatric surgery used to treat obesity and the indications for each one.
3. Discuss the risks of bariatric surgery for treating obesity.
4. Explain the probabilities for weight-loss success following bariatric surgery.
5. Discuss the pros and cons of using bariatric surgery for people who are obese and have type 2 diabetes.
Examination
1. Although revisions to body mass index (BMI) guidelines for gastric surgery are being considered, it is most often performed using the following criteria:
a. BMI at or above 35 (obesity) with repeated failure to manage weight
b. BMI between 30 and 35 with repeated failure to manage serum glucose
c. BMI at or above 40 (extreme obesity) or BMI at or above 35 with two comorbidities
d. Psychological or social issues that preclude diet and exercise regimes to control weight and/or blood sugar
2. What factor(s) should be considered when choosing the type of gastric reduction surgery to be performed on a patient?
a. BMI
b. Age
c. Comorbidities
d. All of the above
3. What type of bariatric surgery is considered the “gold standard”?
a. Roux-en-Y
b. Biliopancreatic diversion
c. Laparoscopic banding
d. Vertical banding
e. Vagal block
4. What initial recommendation is made to gastric reduction surgery patients regarding fluid and food intake?
a. Total amount will depend on body size, but urine should be pale yellow.
b. Limit volume at any given time and eat small meals.
c. Fluids should be consumed with meals.
d. All of the above
e. None of the above
5. Who would be the most appropriate candidate for biliopancreatic diversion surgery?
a. People who are superobese
b. Those who have a history of adequate protein intake
c. People who did not lose weight with a Roux-en-Y bypass
d. All of the above
e. None of the above
6. What is the reported risk of death from bariatric surgery?
a. Greater than 10%
b. About 8%
c. About 6%
d. About 4%
e. Less than 2%
7. Which of the following is not a risk of gastric reduction surgery?
a. Bloating
b. Protein deficiency
c. Constipation
d. Vomiting
e. Vitamin and mineral deficiency
8. What is the mean percentage of excess body weight lost in patients with bariatric surgery?
a. 30%
b. 40%
c. 60%
d. 80%
e. 100%
9. The cure rate for diabetes is extremely high in patients who have undergone Roux-en-Y or biliopancreatic diversion surgeries. What is the likely primary reason for the resolution of the diabetes?
a. Large amount of weight loss
b. Large amount of fat loss
c. Significant reduction in sugar intake
d. Reduction in gut hormone stimulation
e. Large amount of water loss
10. Clinical measurements important in determining whether diabetes has resolved following gastric reduction surgery include:
a. hemoglobin A1c.
b. lipid levels.
c. postprandial glucose levels.
d. a and c
e. All of the above
References
1. Buchwald H, Avidor Y, Braunwald E, et al. Bariatric surgery: A systematic review and meta-analysis. JAMA. 2004;292(14):1724-1737.
2. Dunford M. Principles of bariatric surgery. In: Treating Severe Obesity. Talent, Ore.: Nutrition Dimension, Inc; 2008.
3. Vetter M, Cardillo S, Rickels MR, Iqbal N. Narrative review: Effect of bariatric surgery on type 2 diabetes mellitus. Ann Intern Med. 2009;150(2):94-103.
4. Buchwald H. Management of morbid obesity: Surgical options. J Fam Pract. 2005;Suppl:S10-S17.
5. Brolin RE. Complication of Roux-en-Y gastric bypass for morbid obesity. Current Surgery. 2003;60(2):138-142.
6. Bult MJ, van Dalen T, Muller AF. Surgical treatment of obesity. Eur J Endocrinol. 2008;158(2):135-145.
7. DeMaria EJ. Is gastric bypass superior for the surgical treatment of obesity compared with malabsorptive procedures? J Gastrointest Surg. 2004;8(4):401-403.
8. Buchwald H, Estok R, Fahrback K, et al. Trends in mortality in bariatric surgery: A systematic review and meta-analysis. Surgery. 2007;142(4):621-632.
9. Melvin WS. Roux-en-Y gastric bypass is the operation of choice for bariatric surgery. J Gastrointest Surg. 2004;8:298-400.
10. Prachand VN, Davee RT, Alverdy JC. Duodenal switch provides superior weight loss in the super-obese (BMI ≥ 50 kg/m2) compared with gastric bypass. Ann Surg. 2006;244(4):611-619.
11. Brolin RE. Gastric bypass. Surg Clin North Am. 2001;81(5):1077-1095.
12. Cook CM, Edwards C. Success habits of long-term gastric bypass patients. Obes Surg. 1999;9(1):80-82.
13. 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(3):316-323.
14. Schauer PR, Burguera B, Ikramuddin S, et al. Effect of laparoscopic Roux-en Y gastric bypass on type 2 diabetes mellitus. Ann Surg. 2003;238(4):467-485.
15. Roslin M, Oren JH, Yatco E, Shah PC. PL-205: Abnormal glucose tolerance testing following gastric bypass. Surg Obesity Related Dis. 2009;5(3 Suppl 1):S10.
16. The Diabetes Prevention Program Research Group. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Eng J Med. 2002;346(6):393-403.
17. The Look AHEAD Research Group. Reduction in weight and cardiovascular disease risk factors in individuals with type 2 diabetes: One-year results of the Look AHEAD trial. Diabetes Care. 2007;30(6):1374-1383.
