BACKGROUND: Bariatric surgery results in dramatic weight loss and improves metabolic syndrome and type 2 diabetes (T2DM). However, previous studies have noted that morbidly obese patients with T2DM experience less weight loss benefits than non-diabetic patients following bariatric surgery. We sought to determine longitudinal effects of laparoscopic Roux-en-Y gastric bypass (LRYGB) on percent excess body mass index (BMI) loss (%EBMIL) and clinical metabolic syndrome parameters in patients with T2DM compared with appropriately matched cohort without T2DM. METHODS: Retrospective cohort analysis of T2DM patients (n = 126) to non-T2DM patients (n = 126) matched on age (M = 48.1 ± 9.5), sex (81 % female), race (81 % Caucasian), and pre-surgical BMI (M = 49.3 ± 9.5). Lipids, glucose, hemoglobin A1c, blood pressure, co-morbidities of obesity, medications for co-morbidities, and T2DM medications were collected at baseline, 6 months and 12 months post-surgery. %EBMIL was collected at 1, 3, 6, 9, and 12 months post-surgery. One-way analyses of variance with effect sizes estimates were conducted to compare the two groups. RESULTS: As expected, T2DM subjects had significantly greater pre-surgical HbA1c, blood glucose, blood pressure, and lipid parameters at baseline vs. non-T2DM (all p values of<0.05). At 1, 3, 6, 9, and 12 months after LRYRB, both groups had similar reduction in %EBMIL (p > 0.10). At 6 months, there was a significant reduction in HbA1c, blood glucose, and lipid in the T2DM cohort compared with pre-surgical levels (p < 0.0001). At 12 months, these values were not different to that of the non-T2DM subjects (p > 0.10). CONCLUSIONS: When matched on appropriate factors associated with weight loss outcomes, severely obese patients with T2DM have similar post-LRYGB weight loss outcomes in the first 12 months following surgery compared with non-T2DM patients. Furthermore, T2DM surgical patients achieved significant improvement in metabolic syndrome components.