Clinicians out there – have you ever been asked this question?
I get asked this question at least once a day.
There is an expanding body of data demonstrating the powerful ability of bariatric surgery to improve control of type 2 diabetes, and even put it into remission.  However, we are lacking in long term data on this important topic, with most higher quality data only being available to 2 years post surgery.  For the first time, we now have data from a randomized clinical trial to tell us a little more about what happens to patients with type 2 diabetes, 5 years after bariatric surgery. (Skip to ‘So, my take on this?‘ below if you don’t want the study details)
The study, published this week in The Lancet by Mingrone and colleagues, randomized 60 patients to receive either gastric bypass surgery (n=20), biliopancreatic diversion (BPD, n=20), or medical treatment (n=20) for their type 2 diabetes.  Participants were age 30-60, and had to have type 2 diabetes for at
least 5 years.  Almost half of the patients in the study were using insulin as part of their diabetes treatment.  
The key findings of the study were:
  • At 5 years after surgery, 37% of patients who had gastric bypass, 73% of patients who had BPD, and none of the patients in the medical treatment group, were in remission from their diabetes.
  • About half of patients who achieved diabetes remission at 2 years, had relapsed by 5 years (in other words, their diabetes came back). However, when their diabetes came back, it required less medication and was under better control than before the surgery.
  •   Amount of weight lost did not predict who would go into diabetes remission (or who would relapse).
  • Cardiovascular risk (defined as a composite endpoint of at least 2 parameters including reduction in heart/diabetes drugs and improvement in diabetes, cholesterol, or blood pressure control) decreased more in surgically treated groups.
  • Five major diabetes complications were seen in patients in the medical group, vs one in the gastric bypass group and none in the BPD group.

So, my take on this? These findings support what we have seen in previous nonrandomized 5 year data: bariatric surgery can be quite powerful to put diabetes into remission (with variable effect depending on the type of surgery), but by 5 years, about half of the diabetes cases come back.  This is a small study, but kudos to the study authors, as I know from my own xperiences that it is very difficult to conduct randomized controlled clinical trials in this area.  That the amount of weight loss did not predict the effect of the surgery on diabetes reminds us of the powerful impact of other mechanisms of these surgeries on blood glucose control (for example, changes in gut hormone production).
It’s important to note that while diabetes complications were lower in the surgery group, the surgical and surgically related metabolic complications were (of course) higher in the surgical groups.  These risks were highest in the BPD group, which is a rather dramatic and extensive intestinal bypass procedure.  BPD is not accepted as a standard surgery due to the risk of complications, and in most places BPD is only available in a research setting.
Bariatric surgery can be a powerful and effective treatment for type 2 diabetes for the right individual, who is comfortable with the risk vs benefit profile of surgery, and for whom the benefits clearly exceed the risks.  Patients who experience remission of their diabetes after surgery need to be followed lifelong, as the diabetes can certainly come back.
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