August 2018 Issue
Diabetes Management & Nutrition Guide: Bariatric Surgery's Role in Managing Type 2
By Constance Brown-Riggs, MSEd, RD, CDE, CDN
Vol. 20, No. 8, P. 44
Learn about the different procedures available and strategies for counseling patients.
Obesity is a significant independent risk factor for developing type 2 diabetes, and more than 90% of people with type 2 diabetes are overweight or obese.1 There's a robust body of evidence stating that obesity management can delay the progression from prediabetes to type 2 diabetes and may be beneficial in the treatment of type 2 diabetes.2 Moreover, in overweight and obese individuals with type 2 diabetes, modest and sustained weight loss of just 5% of total body weight has been shown to improve glycemic control and reduce the need for glucose-lowering medications.1,2 Various treatment options for obesity management are available, including but not limited to lifestyle modification, a very low-calorie diet, pharmacotherapy, and bariatric surgery.2 Metabolic and bariatric surgery may resolve or improve type 2 diabetes; these results can occur independently of weight loss.1 Improvements in glycemia after weight loss are most likely to occur early in the natural history of type 2 diabetes when obesity-associated insulin resistance has caused reversible beta-cell dysfunction, but insulin secretory capacity remains relatively preserved.2
This article will provide an overview of surgical interventions for obesity management as treatments for hyperglycemia in type 2 diabetes and as a mechanism of diabetes improvement and remission. Counseling tips and considerations when advising clients and patients on the most appropriate surgical procedure also will be discussed.
What Is Bariatric Surgery?
The term "bariatric surgery" comes from the Greek words baros, which means "weight," and iatrikos, "the art of healing."3 Bariatric surgery refers to any surgical procedure on the stomach or intestines to induce weight loss.
The use of bariatric surgery for the treatment of type 2 diabetes started from a report by Pories and colleagues published in the Annals of Surgery in 1995. Pories' report documents how gastric bypass surgery provides long-term control of obesity and diabetes. Since Pories' report, a substantial body of evidence shows that bariatric surgery is an effective treatment for severe obesity, indicated by a BMI >35 kg/m2, and results in marked improvement of type 2 diabetes control. Metabolic surgery, therefore, is increasingly associated with the treatment of type 2 diabetes, including for patients with a BMI <35 kg/m2.4
"The term 'metabolic surgery' is most commonly used to describe someone who has bariatric surgery with diabetes; however, it also can be used to describe weight loss surgery in a patient who has prediabetes or [is] at risk of diabetes," says Kristen Smith, RDN, bariatric surgery coordinator for Piedmont Healthcare in Atlanta.
Bariatric Surgical Options
The benefits of weight loss must be balanced against the potential risks of bariatric surgery. It's also important to consider both immediate and chronic complications following the different types of surgeries. In the longer term, obesity surgery can lead to malabsorption of micronutrients such as vitamins and minerals—which may result in anemia, a loss of lean mass, an increased risk of kidney stones, and a small risk of acute kidney injury.5
The most common bariatric surgery procedures performed in the United States are gastric bypass, gastric sleeve (also called sleeve gastrectomy), and laparoscopic adjustable gastric band. A fourth surgery, biliopancreatic diversion with duodenal switch, is used less often and won't be discussed within the context of this article.6 Surgical options for weight loss include restrictive procedures and malabsorptive procedures. Each surgery has its advantages and disadvantages.
Gastric bypass—also called Roux-en-Y gastric bypass—is considered the gold standard for weight-loss surgery by the American Society for Metabolic and Bariatric Surgery and the National Institutes of Health.7 It consists of creating a small gastric pouch 20 to 30 mL in volume—about the size of an egg—that's surgically connected to the small intestine.8 The Roux-en-Y gastric bypass is a restrictive and malabsorptive procedure. Weight loss is triggered by several mechanisms. First, the newly created pouch facilitates smaller meals, translating into fewer calories consumed.9 The bypass also results in faster emptying of food, which contributes to malabsorption of nutrients and calories. In addition, the bypass produces changes in the gut hormones that promote satiety and suppress hunger.9
Studies show long-term (>10 years) weight loss after Roux-en-Y to be around 25% to 30% total weight loss and 55% to 70% excess weight loss. However, up to 20% of Roux-en-Y patients may, amid various complications or weight regain, require revisional surgery.4
A common side effect of Roux-en-Y is dumping syndrome. About 85% of patients experience dumping syndrome at some point after surgery with symptoms ranging from mild to severe.9 In Roux-en-Y, the pyloric sphincter is bypassed, resulting in faster emptying of food into the small intestine. Dumping syndrome can occur with intake of refined sugars, high-glycemic carbohydrates, dairy products, fats, and fried foods.9
"When undigested carbohydrates such as sugar reach the small intestine too quickly, extracellular fluid is drawn in to restore isotonicity, and in turn, the patient may experience dumping syndrome. Symptoms include sweating, bloating, cold sweats, tachycardia, emesis, dizziness, hypotension, diarrhea, and/or nausea," says Melissa Majumdar, MS, RD, CSOWM, LDN, CPT, nutrition coordinator at Brigham and Women's Hospital's Center for Metabolic and Bariatric Surgery in Boston.
Individuals may experience early dumping, which occurs in about 70% of patients, or late dumping (5% of patients), Majumdar says. Early dumping occurs 30 to 60 minutes after eating and can last up to 60 minutes. Symptoms include sweating, flushing, lightheadedness, tachycardia, palpitations, desire to lie down, upper abdominal fullness, nausea, diarrhea, cramping, and active audible bowels sounds.9
Late dumping occurs one to three hours after eating. Symptoms are related to reactive hypoglycemia (low blood sugar) and include sweating, shakiness, loss of concentration, hunger, and fainting.9 "Patients may experience reactive hypoglycemia if they have gone more than three to four hours without eating or if they have eaten a meal with refined carbohydrates, especially if the meal lacked protein," Majumdar says.
Often referred to as sleeve gastrectomy or the sleeve, gastric sleeve surgery involves removing part of the stomach and leaving a thin, banana-shaped portion of the stomach connecting the esophagus to the pylorus. Sizing of the sleeve is based on a 32- to 36-French bougie, resulting in approximately 100 mL volume.8 A bougie is a measuring device used to guide the surgeon when dividing the stomach.
Sleeve gastrectomy initially was used as a first-step bariatric procedure for high-risk patients or those with a BMI more than 60 kg/m2 to reduce the risk profile of patients. Once adequate weight loss occurred, a malabsorptive surgery often was performed.10 However, it was discovered that sleeve gastrectomy alone could cause significant weight loss before the second procedure.
Sleeve gastrectomy not only restricts food intake but also increases both gastric emptying and intestinal transit time. As a result of its efficacy for weight loss, relative simplicity, and fewer long-term nutritional problems, sleeve gastrectomy has rapidly become the most commonly performed bariatric/metabolic surgery worldwide.4 Total weight loss of approximately 25% to 30% and excess weight loss of 60% to 70% for as many as 10 years can be achieved. However, a significant drawback of this procedure is the development of reflux esophagitis. Given this possibility, or amid subsequent weight regain, up to 30% of sleeve gastrectomy patients may require revisional surgery.4
Adjustable Gastric Band
In an adjustable gastric band procedure, a silicone band is placed around the stomach at the level of the cardia with an adjustment port placed in the subcutaneous tissue—usually in the epigastric region—connected to the band via silicone tubing.8
Adjustable gastric band is the safest bariatric surgical procedure, but the efficacy is less than that of other bariatric procedures. Once sleeve gastrectomy emerged, it quickly replaced adjustable gastric band in almost every part of the world. Long-term (>10 years) weight loss after adjustable gastric band surgery was approximately 15% of total weight loss and 40% to 45% of excess weight loss. However, up to one-half of adjustable gastric band patients may require revisional surgery in the event of insufficient weight loss.4
Efficacy of Metabolic Surgery in Diabetes
Metabolic surgery is associated with improvements in weight, glycemia, hepatic insulin and peripheral insulin resistance, insulin secretion, blood pressure, lipid profile, inflammation, end-organ damage, and diabetes remission.
Changes in hepatic insulin resistance, peripheral insulin resistance, and insulin secretion are due to increased serum bile acid levels, which stimulate glucagonlike peptide-1 and peptide YY.8 At two years, pancreatic beta-cell function improves in patients with Roux-en-Y gastric bypass but not in those who have had sleeve gastrectomy. Postoperatively, plasma insulin concentration levels are reduced but the postprandial response is exaggerated. These changes occur within days of Roux-en-Y surgery and are associated with the rise in glucagonlike peptide-1 and peptide YY, reduced fasting insulin levels, and increased insulin sensitivity. The changes also are observed in sleeve gastrectomy but to a lesser extent than in Roux-en-Y. In patients with a gastric band, improvements in glycemia, insulin secretion, and insulin resistance are directly related to weight loss.8 Studies show that more than 70% of patients with type 2 diabetes of two years or less in duration achieved a fasting blood glucose level of less than 126 mg/dL through a gastric band.8
The mechanisms for improved blood pressure are multifactorial and may be associated with weight loss, reduced systemic inflammation, increased urinary sodium loss, and restoration of metabolic homeostasis. Research shows blood pressure improves in 73.2% of patients who are still losing weight after bariatric surgery. Serum total cholesterol, triglycerides, and LDL cholesterol decrease while HDL cholesterol increases following bariatric surgery.8
Remission of type 2 diabetes after bariatric surgery was first reported in the late 1980s. Since that time, multiple observational studies have demonstrated significant, sustained improvements in type 2 diabetes among patients with severe obesity (BMI ≥35 kg/m2) after weight loss procedures.11
A meta-analysis involving 19 studies (mostly observational) and 4,070 patients reported an overall type 2 diabetes resolution rate of 78% after bariatric surgery. Resolution typically was defined as becoming "nondiabetic" with normal HbA1c without the use of medications. HbA1c usually improved from baseline by a minimum of 1%, up to 3% following surgery.11
One of the largest and longest weight loss studies is the Swedish Obese Subjects study, a prospective study evaluating the long-term effects of bariatric surgery compared with nonsurgical weight management of severely obese (BMI >34 kg/m2) patients. In the study, the remission rate for type 2 diabetes was 72% at two years and 36% at 10 years compared with 21% and 13%, respectively, for the nonsurgical control patients. Bariatric surgery also was markedly more effective than nonsurgical treatment in the prevention of type 2 diabetes, with a relative risk reduction of 78%.11,12
Strategies for Helping Patients
The increasing prevalence of bariatric surgery makes it likely that dietetics professionals will encounter patients pre- and postbariatric surgery. Following is a list providing best practices when counseling patients regarding bariatric surgery.
• Understand the different metabolic weight loss procedures and who the ideal candidate is for each. According to the American Diabetes Association's Standards of Medical Care in Diabetes — 2018, appropriate surgical candidates are those with a BMI ≥40 kg/m2 (BMI ≥37.5 kg/m2 in Asian Americans), regardless of the level of glycemic control or complexity of glucose-lowering regimens, and in adults with BMI 35 to 39.9 kg/m2 (BMI 32.5 to 37.4 kg/m2 in Asian Americans) when hyperglycemia is inadequately controlled despite lifestyle and optimal medical therapy. Metabolic surgery should be considered as an option for adults with type 2 diabetes and BMI 30 to 34.9 kg/m2 (BMI 27.5 to 32.4 kg/m2 in Asian Americans) if hyperglycemia is inadequately controlled despite optimal medical therapy by either oral or injectable medications (including insulin).
Majumdar says, "From a dietitian's perspective, the ideal candidate is looking for an opportunity to change their life using the tool of metabolic surgery along with the support of their fellow patients and the education and support of the surgery program. An ideal candidate uses surgery as a springboard to adjust diet and lifestyle and possibly change their whole family's take on food and nutrition. They take control of their hunger through the hormonal and appetite adjustments surgery provides and, in the meantime, increase activity and face nonhunger reasons for eating head on."
• Promote protein-rich foods. Depending on an individual's medical condition, type of surgery, and activity level, protein intake recommendations range from 60 to 100 g daily.9 "During a nutrition consult, we analyze a typical eating pattern and measure protein intake. After protein goals are met, we look for a variety of food (nonstarchy vegetables, fruits, whole grains, and healthful fats) just like we would assess any patient," Majumdar says. To improve weight loss, clients should be encouraged to limit foods high in added sugars (eg, cookies, cakes, candy, juice, or other sweets) and refined carbohydrates (eg, white breads, pastas, crackers, refined cereals).9
• Educate clients who choose Roux-en-Y gastric bypass on risk and prevention of dumping syndrome—a common side effect—and hypoglycemia. Majumdar helps her patients understand the "blood sugar roller coaster" that may occur if they go too long without eating or if they eat refined carbohydrates. "The patient should be encouraged to include protein and fiber at all eating events, spacing meals and snacks to every three to four hours," Majumdar says. "If patients are in the habit of forgetting meals, we may use reminder techniques such as timers or apps; we will also discuss snacks and meals for emergencies (shelf-stable foods, protein shakes/bars), and on-the-go eating."
Dumping can occur from consuming added sugars and drinking fluids with meals; however, Majumdar says it's less likely to be the result of consumption of natural sugars such as fruit, milk, and yogurt. "We advise patients to look for protein shakes with less than 20 g total sugar (from added and total sugars), limit added sugars, and choose products with more protein and fiber compared to sugar," says Majumdar, who also encourages patients to wait 30 minutes after eating before drinking to prevent dumping.
Clients also should be informed about other common complaints after surgery, such as nausea, vomiting, anorexia, dehydration, halitosis, constipation, diarrhea, flatulence, and lactose intolerance.
• Meet clients where they are. "Registered dietitians must avoid being 'food police' and establish an approachable environment for lifelong follow-up," Smith says. She suggests offering a long-term support system using a variety of techniques, "whether that's through support groups, check-in telephone calls, or individual counseling sessions."
• Treat both conditions—diabetes and bariatric surgery. Don't assume the patient understands how to manage diabetes. "I sometimes assume a patient has been educated on diabetes and proper eating but find the patient munching on candy to keep blood sugars from falling or drinking juice daily," Majumdar says. "Starting with a clean slate and educating on how making changes in preparation for surgery or postop can help both with surgery success and blood sugar control."
• Check for vitamin deficiencies, as people with morbid obesity have a higher risk of developing them. Studies have shown that 55% to 80% of those with morbid obesity possibly have a vitamin D deficiency, and nearly 50% of patients seeking bariatric surgery have iron deficiency. Vitamin B12 and thiamin deficiencies also have been identified in bariatric surgery candidates. Majumdar suggests nutrition professionals "look closer for deficiencies such as B12 or other B vitamins in patients with diabetes who have been on metformin, both preoperatively and postop."
— Constance Brown-Riggs, MSEd, RD, CDE, CDN, is a national speaker and coauthor of the Diabetes Guide to Enjoying Foods of the World, a convenient guide to help people with diabetes enjoy all the flavors of the world while still following a healthful meal plan.
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2. American Diabetes Association. Obesity management for the treatment of type 2 diabetes: standards of medical care in diabetes — 2018. Diabetes Care. 2018;41(Suppl 1):S65-S72.
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