Bariatric Surgery for Type 2 Diabetes Mellitus

Dr. Bill Quick Health Pro
  • The Annals of Internal Medicine has just published a review of surgical interventions to treat type 2 diabetes, "Effect of Bariatric Surgery on Type 2 Diabetes Mellitus." The authors reviewed published English-language studies where 10 or more diabetic patients had been enrolled, and where diabetes-related outcomes were reported. Ten such studies were identified.


    The authors point out that "Nearly 30% of patients who undergo bariatric surgery have type 2 diabetes, and for many of them, diabetes resolves after surgery (84% to 98% for bypass procedures and 48% to 68% for restrictive procedures). Glycemic control improves in part because of caloric restriction but also because gut peptide secretion changes."

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    That's the good news.

    But the bad news is that "Conclusions about bariatric surgery and diabetes resolution come with an important qualifier: The studies had serious methodological weaknesses. Few are randomized, controlled trials; most surgical outcome studies are uncontrolled case series with considerable missing data. In 1 meta-analysis, one quarter of the studies did not report enrolling consecutive patients and fewer than 50% reported how many enrolled patients provided follow-up data. "

    In other words, the patients seemed to improve, but the study designs and reporting of results were so vague that it's difficult to guess what might have happened to the patients who apparently had the surgery, and didn't improve. One would like to hope they had the same good outcomes, but I guess I'll be skeptical if the data isn't available.


    Which is why I continue to say that any person with diabetes who might be contemplating such surgery should be enrolled in a study that's well-designed, and which has appropriate staff at the study site to assist with perioperative problems, and where you as the patient sign an "Informed Consent Form" (ICF) that you know that you are participating in a study. Such an ICF is different from the usual surgical consent forms, and should describe clearly the anticipated benefits and possible risks, whether the sponsor of the trial will pay for your medical and surgical care, that you have freedom to withdraw from the study at any time, confidentiality and privacy issues, and lots more. An Institutional Review Board (IRB) should be overseeing the conduct of the trial, and have authority to demand changes in the trial if patient safety is at risk.

    Ideally, the best study from a scientific viewpoint (although perhaps difficult to justify ethically) would be to randomize patients into several groups, and compare the outcomes. If you signed the informed consent, and met the inclusion and exclusion criteria for the study, you would be randomly assigned to one of the following groups:

    1) receiving dietary and lifestyle advice but no surgical intervention.
    2) receiving dietary and lifestyle advice and surgical intervention.
    3) receiving dietary and lifestyle advice and sham surgical intervention. If in this group, you would be wheeled into the operating room, and have an incision in your belly identical to if you were going to have "real" surgery, but the surgeon would not change anything internally.

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    Why do I mention sham surgery? Because in the 1950's, there was a popular surgical procedure to treat angina pectoris (cardiac chest pain) in which the internal mammary artery was tied off. But then, a surgeon named H.K. Beecher described the placebo effect of such surgery in a classic paper following a randomized trial of internal mammary artery ligation versus a sham operation. Thereafter, this surgical procedure was no longer done: it was the placebo effect, not the tying off of an artery, that resulted in the improvement.

    I think that the current procedures for surgical treatment of diabetes fall into much the same category: the desire of the patient to succeed in weight loss as well as to obtain improved diabetes control needs to be accounted for, at least by a subgroup receiving identical lifestyle interventions without surgery, and with the instructors blinded to whether the patient did or did not have the surgery. And if sham surgery could be approved by the IRB approving the conduct of the trial, then include a sham surgery subgroup in the study.

    So, again, my advice to people asking about having surgery to treat their diabetes: Realize that this is experimental surgery. And as such, this surgery should only be undertaken in a clinical trial setting, with a highly qualified team, and appropriate safeguards so that subsequent publication of the results can help future physicians to thoroughly understand the advantages and disadvantages of such surgery.

Published On: January 23, 2009