Metabolic surgery for the treatment of type 2 diabetes in patients with BMI <35 kg/m2: an integrative review of early studies.

Type 2 diabetes mellitus (T2DM) resolution in morbidly obese patients following metabolic surgery suggests the efficacy of T2DM surgery in non-morbidly obese patients (body mass index [BMI] <35 kg/m(2)). This literature review examined research articles in English over the last 30 years (1979-2009) that addressed surgical resolution of T2DM in patients with a mean BMI <35. Weighted and simple means (95% CI) were calculated to analyze study outcomes. Sixteen studies met inclusion criteria; 343 patients underwent one of eight procedures with 6-216 months follow-up. Patients lost a clinically meaningful, not excessive, amount of weight (from BMI 29.4 to 24.2; -5.1), moving from the overweight into the normal weight category. There were 85.3% patients who were off T2DM medications with fasting plasma glucose approaching normal (105.2 mg/dL, -93.3), and normal glycated hemoglobin, 6% (-2.7). In subgroup comparison, BMI reduction and T2DM resolution were greatest following malabsorptive/restrictive procedures, and in the preoperatively mildly obese (30.0-35.0) vs overweight (25.0-25.9) BMI ranges. Complications were few with low operative mortality (0.29%). Novel and/or known mechanisms of T2DM resolution may be engaged by surgery at a BMI threshold <or=30. The majority of low-BMI patients experienced resolution of laboratory and clinical manifestations of T2DM without inappropriate weight loss.