Bariatric surgery for type 2 diabetes: Reaching too far?

Although bariatric surgery is becoming an increasingly accepted option to reverse type 2 diabetes, lifestyle interventions, including smoking cessation, improved nutrition, and increased physical activity, coupled with appropriate pharmacotherapy, remain the mainstays for the management of type 2 diabetes, says Bernard Zinman, MD.

"None of us would debate the notion that someone who has massive obesity, BMI [body mass index] in the 35 to 45 kg/m² range, sleep apnea, congestive heart failure, arthritis, metabolic syndrome, type 2 diabetes, has failed traditional forms of nutritional counseling, benefit tremendously from bariatric surgery," he says. "The real question is, people who are not terribly obese who also have type 2 diabetes, should they be treated with surgery?"

In arguing against bariatric surgery in the latter group, he says there is little underlying evidence that the pathophysiology of type 2 diabetes is the result of a maladaptive gastrointestinal anatomy.

Type 2 diabetes is characterized by insulin resistance. "The problem is another kind of insulin resistance," says Dr. Zinman, professor of medicine, University of Toronto. "The kind of insulin resistance that we’re often faced with is a reduced action of insulin due to the resistance of providers to prescribe insulin and/or to prescribe sufficient insulin in an appropriate manner to achieve glycemic targets."

The problem is clinical inertia, he says. The traditional stepwise approach to managing type 2 diabetes has been a "treat to failure" approach, in which medications are added only when the currently prescribed one(s) loses efficacy in controlling glycemia.

In support of aggressive pharmacotherapy is the American Diabetes Association, which recommends in its guidelines the rapid addition of medications and transition to new regimens when target glycemic goals are not achieved or sustained and early addition of insulin for those who do not reach target goals.

Unfortunately, patients with a hemoglobin A_1c level greater than 8% while on metformin therapy wait an average of 14 months before an additional medication to improve glucose control is prescribed, and the wait on a sulfonylurea is even longer at 20 months.

Substantial concern remains with bariatric surgery, Dr. Zinman notes. These include bleeding, infection, additional surgeries, gallstones, gastritis, vomiting, iron or vitamin deficiencies, calcium deficiency, dumping syndrome, and bowel obstruction, among others. Further, well-designed controlled clinical trials evaluating the efficacy, durability, and safety of bariatric surgery are lacking. Most of the studies that have been conducted to show resolution of diabetes with surgery have major methodological weaknesses. Also, the mechanisms responsible for the improved metabolic control with bariatric surgery are not understood.