What to Know About Bariatric Surgery for Type 2 Diabetes

The term bariatric is derived from the Greek words for “weight” and “to treat.” Originally, as its name denotes, this form of surgery was aimed at helping people manage obesity. But as medical science’s understanding of bariatric surgery improved, experts recognized that these procedures could also help people with obesity-related health conditions, including Type 2 diabetes.

“In 1999 when I was a junior resident in general surgery, I was struck by the observation that patients who had this type of surgery were very rapidly seeing improvement in their diabetes,” says Dr. Francesco Rubino, who is now chair of metabolic and bariatric surgery at King’s College London. “Even patients who had very severe diabetes would get to normal levels of blood sugars and could stop taking medication.” He wasn’t the only one noticing these effects, which were supported by formal research.

One early study from researchers at East Carolina University found that 83% of patients with Type 2 diabetes who underwent gastric bypass surgery experienced long-term remission of their disease. Despite these sorts of dramatic clinical observations, surgery at that time was not considered a primary treatment option for Type 2 diabetes. It was also assumed, Rubino says, that any diabetes improvements were caused exclusively by reductions in body weight. “But it always seemed to me like the magnitude of improvement was too much just to be the byproduct of weight loss,” he says. In some cases, a person’s diabetes improvements would come even before they’d lost significant weight.

Flash forward more than 20 years, and experts continue to debate precisely how bariatric procedures benefit people with Type 2 diabetes. But today, there is no question that these procedures do provide a benefit. Recent trials have found that bariatric surgery is associated with better patient outcomes than non-surgery treatments alone. In 2017, the results of one long-term trial, published in the New England Journal of Medicine, found that adding bariatric surgery to non-surgical diabetes care led to major improvements in patient outcomes. People who underwent surgery were more than three times as likely to achieve normal blood sugar scores one year after treatment. They were also less likely to be on glucose-lowering medications, and they reported greater quality-of-life improvements.

“Surgery can actually put diabetes into remission, and it’s safe and cost-effective compared to standard non-surgical care,” says Dr. Carel Le Roux, a professor at University College Dublin who studies bariatric surgery for people with diabetes. “It’s currently the best treatment we have for Type 2 diabetes, and I’m an internal medicine doctor, not a surgeon, so I have no vested interest in talking up surgery.” Le Roux says there’s no question that bariatric procedures should now be considered a primary treatment for Type 2 diabetes, and that too few people who are eligible for these operations are getting them. However, he adds that surgery is “not a silver bullet,” and not everyone with Type 2 diabetes is a candidate.

Here, Le Roux and other experts discuss the latest in bariatric surgery for Type 2 diabetes, including the benefits and risks, the procedures themselves, and how combining surgery with medication may ultimately provide the best long-term results.

How does bariatric surgery benefit people with diabetes?

It’s the million-dollar question. And it has more than one correct answer.

“My view is that weight loss is the dominant mechanism, but clearly there are also other mechanisms at play,” says Le Roux. Type 2 diabetes is a disease of too little insulin and too much blood sugar. Excess body weight increases the amount of insulin needed to manage the blood’s sugar levels, and so it exacerbates the imbalances that give rise to diabetes. There’s also evidence that adipose (fat) cells release byproducts that may damage the pancreas, which is where insulin is produced. These are just some of the reasons why losing weight is associated with diabetes improvements.

But something else—something beyond these weight-loss benefits—is clearly going on. “We see some individuals who are on hundreds of units of insulin leave the hospital following surgery requiring no insulin, and that predates weight loss,” says Dr. Andrew Kraftson, a clinical associate professor and director of the post-bariatric program at the University of Michigan. “This is a bit of a controversial area, but some data suggest that there are unique properties to the surgery itself that produce metabolic benefits.”

The most common bariatric procedures for people with Type 2 diabetes are Roux-en-Y gastric bypass surgery and sleeve gastrectomy. Both procedures involve shrinking the size of the stomach, either by removing a portion of it (sleeve gastrectomy) or dividing it into two sections and connecting the smaller of the two portions to the small intestine (gastric bypass). “It’s clear that the stomach and the intestine are not just a digestive organ, but also an endocrine organ,” Rubino says. “The gastrointestinal tract produces a huge number of hormones, and all of them are involved in sugar metabolism and insulin production.” Furthermore, he says that bariatric surgeries affect the stomach and gut’s populations of microbes, which themselves produce metabolites that play a role in sugar metabolism. “These are just a few of the mechanisms that may explain why operating on the gut can exert such a huge influence on diabetes even absent weight loss,” he says.

In fact, Rubino and other health care professionals who treat people with diabetes have begun referring to bariatric surgery as “metabolic surgery” in order to emphasize that it’s not all about reducing body weight.

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Who should consider bariatric surgery

Right now, the criteria are fairly straightforward. The National Institutes of Health guidelines say that anyone with Type 2 diabetes and a BMI of 35 or higher is a candidate. If your BMI is between 30 and 35 and your diabetes isn’t responding well enough to medications and lifestyle changes, surgery may also make sense. However, in this lower-BMI group, insurance may not pay for the procedure. “Insurance coverage remains a barrier for folks with a lower BMI,” Kraftson says. But even for people who meet all the insurance criteria, only a small percentage are undergoing surgery. “We know bariatric surgery is underutilized,” he says. “Only 1-2% of eligible patients actually have it, so it’s something we need to promote more.”

Le Roux echoes his sentiments. He says that anyone with Type 2 diabetes who has been on medications and hasn’t gotten their blood sugar under control should be considered for surgery, regardless of BMI. “I think surgery should be on the table and being discussed for a lot more patients,” he adds.

Apart from hurdles surrounding insurance coverage, Kraftson says that other factors may be preventing metabolic surgery from really taking hold as a treatment for diabetes. Obesity is a stigmatized disease, he says, and some people may have an aversion to undergoing a surgical procedure that was traditionally performed only on those with severe obesity. “Also, people focus on the one person they know who had [the surgery] and regained all the weight,” he says.

While that’s not the experience of most patients, it can happen. “The potency of the surgery does wane over time, and some people do regain weight or have a reactivation of their diabetes,” Kraftson says. One 2020 study found that, three to six years following a sleeve gastrectomy or Roux-en-Y gastric bypass procedure, about one-quarter of patients had regained their weight. “A majority of people only need surgery and then the job is done,” says Le Roux. “But there’s a subset of people who either don’t have a good response, or they have a relapse later.” Among people who have the procedure at a younger age—something that is increasingly common as Type 2 diabetes rates increase in people under 40—weight regain or diabetes relapse may be more likely.

The surgery comes with additional risks and costs. “Approximately 1 in 20 people will have a significant complication,” Le Roux says. Those include gastrointestinal bleeding, infections, or leakage. Embolisms or thromboses, which can be life-threatening, are also possible. “All these tend to happen early on, which is why we keep people in the hospital for one or two nights,” he says.

Finally, metabolic surgery requires major lifestyle adjustments. Following the surgery, people must adopt a specialized diet and exercise regimen to maintain health and facilitate weight loss. Eating too much or too quickly can cause symptoms such as gut cramps, pain, and diarrhea. Also, things a person once loved to eat—even healthy foods—may not taste the same or provide the same pleasure. Alcohol is initially off limits. Even after full recovery, people have to be very careful with how they drink. Finally, to avoid nutrient deficiencies, it’s necessary to take several daily supplements. “You normally have to take a multivitamin twice a day, and calcium three times a day, so it’s a lot of work to prevent these deficiencies,” Kraftson says.

Even in people who do everything right, surgery is not always successful. Understanding why some people don’t respond well—and figuring out how to prevent a poor response—is “the cutting edge” of today’s research on surgery for Type 2 diabetes, Le Roux says.

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The future: A mix of surgery and medications?

One of the big stories in both obesity and diabetes care is the arrival of new injectable drug medications that, at least in clinical trials, have been shown to help people with obesity lose significant weight—in some cases 20% or more. “Lots of people think these drugs will be the death of bariatric surgery,” Le Roux says. “I don’t agree, and I think a large number of patients will have surgery plus medications, but at a lower dose.”

The majority of people who undergo surgery—roughly 70% of patients, he says—enjoy sustained weight loss and diabetes remission without the aid of drugs. But for the subset of people who either don’t have a good response or who eventually relapse, some of these new medications may prove helpful. “The answer may not be surgery instead of medicine, but medicine with surgery,” he says.

Others share his view. “We find that some of these weight-control medications work synergistically with surgery, so they enhance portion control and satiety,” Kraftson says. It’s yet to be seen whether the newest drugs enhance patient outcomes when combined with metabolic surgery. But this is a distinct possibility, and could become the standard of care for people with both obesity and hard-to-control diabetes.

Rubino says the big message for people with Type 2 diabetes is that surgery may provide the best hope for lasting remission. “We’re taught that Type 2 diabetes is a chronic, progressive, irreversible disease,” he says. “But full remission is possible with surgery, and it’s possible in a majority of patients.”