Revisiting the Role of BMI in the Guidelines for Bariatric Surgery.

The high and growing prevalence of obesity worldwide, combined with the corresponding increase in the prevalence of diabetes, and further combined with the relatively poor long-term success of conservative obesity treatment, led to a sharp escalation in the use of bariatric surgery, the prevalence of which has tripled in the past decade (1). A total of 468,609 bariatric procedures were performed worldwide in the year 2013 according to the International Federation for the Surgery of Obesity and Metabolic Disorders (IFSO) survey (1), and this extraordinary acceptance, by both patients and physicians, stems from the fact that these procedures are not only efficient for weight loss but also effective in treating the metabolic syndrome in people with obesity. Bariatric surgery, as its name suggests, was originally designed to reduce weight, with current eligibility criteria being BMI $40 or $35 kg/m with comorbidities, while lower BMIs are excluded. However, its significant beneficial impact on several components of the metabolic syndrome, particularly uncontrolled diabetes, led to the introduction of bariatric surgery as a means to treat diabetes two to three decades ago (2–4), yet only in obese individuals. Since then, along with the improvement in surgical technique, bariatric surgery performed in morbidly obese individuals established itself not only as the most effective means of treating diabetes but also as a “cure” to the disease in a significant proportion of the cases (5–7). The excellent results of bariatric surgery in improving glucose homeostasis in obese patients with type 2 diabetes led to the coinage of the term “metabolic surgery” (8), wherein amelioration of hyperglycemia in obese patients with type 2 diabetes has been observed even before a significant weight loss has taken place (9). Several mechanisms were offered to explain this dramatic impact of bariatric surgery on glucose homeostasis in patients with diabetes, including changes in the secretion of glucagon-like peptide 1, fibroblast growth factor 19, and bile acid as well as in the gut microbiota (10–13). Although the exact mechanisms that lead to postsurgical remission of type 2 diabetes are not fully understood, the fact that the metabolic improvement seems to be, at least partially, weight loss independent provides sufficient basis to consider “bariatric” surgery for nonmorbidly obese or even nonobese metabolically impaired patients. Before we enter a debate over bariatric surgery as a treatment for the metabolic syndrome, especially uncontrolled diabetes, in less obese individuals, it is important to review the factual and observational insights stemming from two decades of accumulating experience. In a large meta-analysis summarizing 621 studies with morbidly obese patients with diabetes undergoing bariatric surgery, a dramatic impact of surgery on diabetes outcomes with an average 2.1% decrease in HbA1c and a diabetes remission rate of 78.1% has been found (14). However, this work is based on cohorts lacking a longterm follow-up period. In trials where the follow-up period is extended to$5 years, diabetes remission rate is lower, and a significant percent of the patients in remission eventually relapse (15–17). The SwedishObese Subjects (SOS) study, providing 15 years of follow-up (17), has shown a high rate of diabetes relapse after an initial remission (occurring in.50% of the patients) and has also shown that the impact of bariatric surgery on long-term diabetes remission is reserved for patients with a short duration of disease. However, bothmicrovascular andmacrovascular complications in this cohort were significantly lower in operated patients compared with the control group, suggesting that the benefits of bariatric surgery may encompass important advantages beyond diabetes remission. Institute of Endocrinology, Sheba Medical Center, Ramat Gan, Israel Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel Internal Medicine D and Obesity Clinic, Hasharon Hospital, Rabin Medical Center, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel