The prevalence of morbid obesity in Canada has risen almost 5 fold in the past three decades. Surgery remains the cornerstone of treatment of obesity and related comorbidities such as type-2 diabetes. Bariatric/metabolic procedures can be classified into 2 main categories: a) those that cause restriction, and b) those that add a malabsorptive component to restriction. Currently sleeve gastrectomy (SG), which is a purely restrictive operation, is the most frequently performed procedure in North America.

Interestingly, combined restrictive/malabsorptive procedures such as Roux-en-Y gastric bypass (RYGB) or biliopancreatic diversion with duodenal switch (BPD-DS) are more effective procedures when compared to purely restrictive ones. Moreover, the conventional BPD-DS procedure has been shown to be significantly more effective than RYGB in achieving durable weight loss and resolving comorbidities such as type-2 diabetes. Despite superior outcomes, the performance of BPD-DS is highly institution dependant and comprises less than 5% of the annual bariatric procedures performed worldwide.

Common reservations against BPD-DS are related to the side effects of the procedure, and include frequent bowel movements, flatulence, fat, micronutrient and protein malnutrition. Furthermore, longer operative times and surgical technical challenges are also reasons for lower prevalence of the BPD-DS procedure.

Single anastomosis duodeno-ileal bypass with sleeve gastrectomy (SADI-S) is a modification of the conventional BPD-DS that potentially addresses many of these concerns. In addition, it is a suitable second-stage or salvage procedure for severely obese patients with inadequate weight loss or resolution of obesity-related comorbidities after SG. Despite showing excellent results of up to 5 years with acceptable postoperative morbidity, all the literature on SADI-S originates from a single center and has not been compared directly with BPD-DS. Hence, the investigators aim to evaluate the feasibility, safety, and postoperative outcomes of SADI-S as it compares to conventional BPD-DS in morbidly obese patients.

This project has three specific aims:

1. To evaluate feasibility and short-term safety of SADI-S.
2. To evaluate short and long-term beneficial outcomes.
3. To evaluate and compare long-term morbidity.

The prevalence of morbid obesity in Canada has risen almost 5 fold in the past three decades. Surgery remains the cornerstone of treatment of obesity and related comorbidities such as type-2 diabetes. Bariatric/metabolic procedures can be classified into 2 main categories: a) those that cause restriction, and b) those that add a malabsorptive component to restriction. Currently sleeve gastrectomy (SG), which is a purely restrictive operation, is the most frequently performed procedure in North America.

Interestingly, combined restrictive/malabsorptive procedures such as Roux-en-Y gastric bypass (RYGB) or biliopancreatic diversion with duodenal switch (BPD-DS) are more effective procedures when compared to purely restrictive ones. Moreover, the conventional BPD-DS procedure has been shown to be significantly more effective than RYGB in achieving durable weight loss and resolving comorbidities such as type-2 diabetes. Despite superior outcomes, the performance of BPD-DS is highly institution dependant and comprises less than 5% of the annual bariatric procedures performed worldwide.

Common reservations against BPD-DS are related to the side effects of the procedure, and include frequent bowel movements, flatulence, fat, micronutrient and protein malnutrition. Furthermore, longer operative times and surgical technical challenges are also reasons for lower prevalence of the BPD-DS procedure.

Single anastomosis duodeno-ileal bypass with sleeve gastrectomy (SADI-S) is a modification of the conventional BPD-DS that potentially addresses many of these concerns. In addition, it is a suitable second-stage or salvage procedure for severely obese patients with inadequate weight loss or resolution of obesity-related comorbidities after SG. Despite showing excellent results of up to 5 years with acceptable postoperative morbidity, all the literature on SADI-S originates from a single center and has not been compared directly with BPD-DS. Hence, the investigators aim to evaluate the feasibility, safety, and postoperative outcomes of SADI-S as it compares to conventional BPD-DS in morbidly obese patients. Our project has three specific aims:

1. To evaluate feasibility and short-term safety of SADI-S. The investigators will assess operative parameters (e.g. procedure time, inadvertent injuries, need for conversion to laparotomy, and transfusion of blood products) and 30-day postoperative adverse events (e.g. length of stay, superficial/deep surgical site infection, leak, venous thromboembolism (VTE), need for reintervention and readmission).
2. To evaluate short and long-term beneficial outcomes. The investigators will evaluate and compare excess weight loss, resolution of type-2 diabetes and other comorbidities, and changes in quality of life at 1, 6, 12 months and yearly thereafter for both groups.
3. To evaluate and compare long-term morbidity. The investigators will evaluate and compare both groups at 6, 12 months and yearly thereafter following surgery for long-term morbidities (e.g. frequency of bowel movements, fat malabsorption, micronutrient and protein-calorie malnutrition, need for supplemental nutrition, internal/incisional hernia, and gastro-esophageal reflux).

Inclusion Criteria:

Participants must meet ALL of the following inclusion criteria:

• Age ≥18 years and ≤60 years
• Fulfill criteria for bariatric surgery as coined by National Institutes of Health
• Give written informed consent

Exclusion Criteria:

Participants who meet any of the following criteria at the time of the baseline visit are excluded from the study:

• Presence of the following baseline comorbidities:
• Congestive heart failure (CHF),
• Chronic kidney disease (CKD) stage 3-5 (or GFR <60 ml/min per 1.73 m2),
• Inflammatory bowel disease (IBD),
• Pulmonary hypertension (PHTN),
• Cirrhosis.
• Severe gastroesophageal reflux disorder (GERD) +/- presence of any Barrett's disease
• Individuals who were found by any member of the multidisciplinary team (nutritionist, nurse, psychologist, and surgeon) to be at risk for lack of support and poor compliance (e.g. ≥2 missed appointments without a valid justification)