New research shows that bariatric surgery (also known as obesity surgery) is much more effective than an intensive lifestyle/medication intervention at reversing type 2 diabetes in patients with only mild-to-moderate obesity. The study is published in Diabetologia (the journal of the European Association for the Study of Diabetes [EASD]) and is by Dr David E. Cummings, Department of Medicine, University of Washington, Seattle, WA, USA, and colleagues including at the Group Health Research Institute, Seattle, WA, USA. The study underlines that it may no longer be appropriate to consider someone for bariatric surgery based primarily on just their body mass index, but also on whether they have diabetes.
Mounting evidence indicates that Roux-en-Y gastric bypass (RYGB) - a type of bariatric surgery - can reverse type 2 diabetes, through mechanisms beyond just reduced food intake and body weight. Large observational studies report that in severely obese individuals, bariatric surgery is associated with long-term reductions in all major cardiovascular disease (CVD) risk factors, CVD events such as heart attacks and strokes, cancer and all-cause mortality, including a 92% decrease in diabetes-related deaths. However, since these data are from observational studies, it is impossible to be certain of the size of the effect of surgery without randomised controlled trials comparing surgical with non-surgical care.
Thus in this study, the authors compared RYGB to an intensive lifestyle and medical intervention (ILMI) for type 2 diabetes, including among only mildly obese patients with a BMI <35 kg/m2 (above 30 kg/m2 is considered obese, so 30-35 BMI is the least severe obesity category among white people). The study was named the CROSSROADS trial (Calorie Reduction Or Surgery: Seeking to Reduce Obesity And Diabetes Study).
By use of a shared decision-making recruitment strategy targeting the entire at-risk population within an integrated community healthcare system, the researchers screened 1,808 adults meeting inclusion criteria (age 25-64, with type 2 diabetes and a BMI 30-45 kg/m2). Due to a wide range of factors including each patient's pre-held beliefs about what might or might not be successful for them, it was very difficult to get patients to agree to be randomised to surgery or non-surgery. As a result, only 43 were randomly allocated in a 1:1 ratio to RYGB or ILMI. The lifestyle intervention involved 45 minutes or more of aerobic exercise 5 days or more per week, a dietician-directed weight- and glucose-lowering diet, and optimal diabetes medical treatment for 1 year. Although treatment allocation could not be blinded, outcomes were determined by a blinded adjudicator. The primary outcome was diabetes remission at 1 year (HbA1c <6.0% and not taking any diabetes medicines).
A total of 23 volunteers were assigned to RYGB and 20 to ILMI. Of these, 11 withdrew before receiving any intervention, leaving 15 in the RYGB group and 17 in the IMLI group to be analysed for the whole year. The groups were equivalent regarding all baseline characteristics, except that the RYGB cohort had by chance a longer diabetes duration (11.4 versus 6.8 years).
Weight loss at 1 year was 25.8% for RYGB versus 6.4% ILMI, respectively. The ILMI exercise programme yielded a 22% increase in exercise capacity, whereas after RYGB exercise capacity was unchanged. Diabetes remission at 1 year was 60% with RYGB versus 6% with ILMI. The HbA1c decline over 1 year was only modestly more after RYGB than ILMI: from 7.7% to 6.4% vs 7.3% to 6.9%, respectively; however, this drop occurred with significantly fewer or no diabetes medications after RYGB. No life-threatening complications occurred in either group.
The authors say: "Compared with the most rigorous intensive lifestyle and medical intervention yet tested against surgery in a randomised trial, RYGB yielded greater type 2 diabetes remission in mild-to-moderately obese patients recruited from a well-informed, population-based sample."
They add: "These results apply to patients with a BMI of 30-35 kg/m2, as well as to more obese patients, and our study and others show that neither baseline BMI nor the amount of weight lost dependably predicts diabetes remission after RYGB, which appears to ameliorate diabetes through mechanisms beyond just weight reduction. These findings call into serious question the longstanding practice of using strict BMI cut-offs as the primary criteria for selection for bariatric surgery among patients with type 2 diabetes."