Bariatric surgery is effective in the management of type 2 diabetes (T2D) and obesity; however, it is not clear whether Roux-en-Y gastric bypass (GBP) or sleeve gastrectomy (SG) is the most effective procedure. This review compared T2D remission and weight loss in patients with T2D after GBP or SG. All human SG or GBP studies published in English between 1 Jan 2007 and 30 April 2012 reporting on BMI and T2D outcomes were included. Analyses were performed separately for the most frequent distinct time points reported after surgery. A total of 21 prospective (three randomised control trials) and 12 retrospective studies, involving 1375 patients met eligibility criteria. T2D remission defined by hemoglobin A1c of <6.5 % for GBP and SG respectively was 67 and 56 % at 3 months, 76 and 68 % at 12 months, and 81 and 80 % at 36 months. Greater percent excess BMI loss occurred at 12 months (72.5 % after GBP and 66.7 % after SG) compared with 3 months (45.9 % after GBP and 25.9 % after SG). There was no significant difference in either T2D remission or weight loss with GBP compared with SG. Both GBP and SG result in similar early remission of T2D in 67 and 56 % of patients at 3 months respectively with modest additional T2D remission with time, although weight loss with both procedures increase substantially between 3 and 12 months post-operatively. Further randomised controlled trials comparing SG and GBP in patients with T2D using comparable definitions of diabetes remission with long-term follow-up are needed to evaluate relative benefits.