Intervention(s) and comparator(s)	Participants included in analysis [N]a	Left study due to adverse events [N (%)]	Total complications [N (%)]	Late complications [N (%)]
Angrisani 2007	Laparoscopic Roux‐en‐Y gastric bypass	24c	‐	‐	‐
	Laparoscopic adjustable gastric banding	26c	‐	‐	‐
Aasheim 2009	Laparoscopic Roux‐en‐Y gastric bypass	‐	‐	‐	9 (29.0)
	Laparoscopic biliopancreatic diversion with duodenal switch (LDS)	‐	‐	‐	12 (41.0)
Demerdash 2013	Laparoscopic Roux‐en‐Y gastric bypass	16d	‐	‐	‐
	Laparoscopic adjustable gastric band	18d	‐	‐	‐
Dixon 2008	Laparoscopic gastric banding in addition to the conventional therapy	30e	‐	‐	‐
	Conventional therapy	30e	‐	‐	‐
Dixon 2012	Laparoscopic adjustable gastric banding and lifestyle programme	30e	‐	‐	‐
	2‐year conventional weight‐loss programme and lifestyle programme	30e	‐	‐	‐
Hedberg 2012	Open biliopancreatic diversion with duodenal switch	24f	‐	‐	‐
	Open Roux‐en‐Y gastric bypass	23f	‐	‐	‐
Himpens 2006	Laparoscopic gastric banding	40f	‐	‐	‐
	Laparascopic isolated sleeve gastrectomy	40f	‐	‐	‐
Ikramuddin 2013	Laparoscopic Roux‐en‐Y gastric bypass + lifestyle programme with medical management	60g	‐g2	‐	‐
	Lifestyle programme with medical management	60g	‐	‐	‐
Karamanakos 2008	Laparoscopic Roux‐en‐Y gastric bypass	30h	‐	‐	‐
	Laparoscopic sleeve gastrectomy	30h	‐	‐	‐
Keidar 2013	Laparoscopic Roux‐en‐Y gastric bypass	22h	‐	‐	‐
	Laparoscopic sleeve gastrectomy	19h	‐	‐	‐
Lee 2011	Simplified laparoscopic mini‐gastric bypass with duodenum exclusion	30e	0 (0)	‐	1 (3.3)
	Laparoscopic sleeve gastrectomy without duodenum exclusion	30e	0 (0)	‐	1 (3.3)
Liang 2013	Usual care	36i	‐	‐	‐
	Usual care + exenatide	34j	‐	‐	‐
	Laparoscopic Roux‐en‐Y gastric bypass	31j	‐	‐	‐
Mingrone 2012	Gastric bypass	20h	1 (5.0)	‐	3 (15)
	Medical therapy	20h	‐	‐	‐
Nguyen 2009	Laparoscopic Roux‐en‐Y gastric bypass	111k	‐	‐	43 (38.7)
	Laparoscopic adjustable gastric banding	86k	‐	‐	10 (11.6)
Nogués 2010	Laparascopic Roux‐en‐Y gastric bypass	7e	‐	‐	‐
	Laparoscopic sleeve gastrectomy	8e	‐	‐	‐
O'Brien 2006	Laparoscopic adjustable gastric band	39k	‐	‐	‐
	Intensive non‐surgical programme	31k	‐	‐	‐
Paluszkiewicz 2012	Open Roux‐en‐Y gastric bypass	‐	‐	‐	‐
	Laparoscopic sleeve gastrectomy	‐	‐	‐	‐
Peterli 2012	Laparoscopic Roux‐en‐Y gastric bypass	110l	‐	‐	‐
	Laparoscopic sleeve gastrectomy	107l	‐	‐	‐
Praveen Raj 2012	Laparoscopic duodenojejunal bypass with sleeve gastrectomy	28e	‐	‐	‐
	Laparoscopic Roux‐en‐Y gastric bypass	29e	‐	‐	‐
Schauer 2012	Intensive medical therapy alone	41k	0 (0)	‐	‐
	Intensive medical therapy plus laparoscopic Roux‐en‐Y gastric bypass	50k	0 (0)	‐	‐
	Intensive medical therapy plus laparoscopic sleeve gastrectomy	49k	1 (2.0)	‐	‐
Sharma 2013	Laparoscopic gastric imbrication	12d	‐	‐	‐
	Laparoscopic sleeve gastrectomy	14d	‐	‐	‐
Vix 2013	Laparoscopic Roux‐en‐Y gastric bypass	44d	‐	‐	‐
	Laparoscopic sleeve gastrectomy	48d	‐	‐	‐
"‐" denotes not reported aNot all of the studies used the ITT population in the adverse events analyses; footnotes show the population on which each of the analyses were based cStudy completers dNumber of completers eITT population fThis is the randomised n; unclear if analyses were ITT or not gITT population (missing data included by multiple imputation) g2All participants were included in the analysis; 3 were lost to follow‐up in each group but reasons not stated hThis is the randomised n iAnalysis population after dropouts (not ITT) ‐ however there were no dropouts in this group jAnalysis population after dropouts (not ITT) kNumber included in the analyses; analyses were not ITT lITT population; analyses based on one year follow‐up data and all participants completed one year follow‐up CONSORT: consolidated standards of reporting trials; ITT: intention to treat