Obesity and inactivity are responsible for 30,000 deaths per year in England and 365,000 deaths per year in the US.     The incidence of severe obesity is increasing at a rapid rate, and this has resulted in a drastic increase in bariatric operations worldwide. Successful obesity surgery has been shown in large-scale prospective trials to result in improved quality of life and a decreased risk of death for people with morbid obesity.       In addition, bariatric surgery (also referred to as metabolic surgery) is being investigated as a possible primary therapy for type 2 diabetes. Results from randomised controlled trials and systematic reviews with meta-analyses have shown superior glycaemic control with bariatric surgery compared with conventional medical therapy alone in people with obesity and type 2 diabetes.      Furthermore, guidelines from national and international organisations, such as the American Diabetes Association,  the UK-based National Institute for Health and Care Excellence,  and the International Diabetes Foundation,   recommend the use of bariatric surgery in people with obesity and type 2 diabetes who have inadequate glycaemic control on optimal medical therapy alone.
The mechanism of action of bariatric surgery for obesity is not fully understood at present but is felt to include gastric volume restriction, malabsorption, and hormonal changes. 
After bariatric surgery, patients may present to clinics, emergency departments, or a hospital other than the one where they had the operation. Thus, it is necessary to be knowledgeable about the common complications.  The obese abdomen may be difficult to examine and can mask typical signs of sepsis. Careful attention to vital signs, examination findings, and any deviation from expected post-operative course is essential.
In order to help patients sustain weight loss after bariatric surgery, regular self-monitoring and frequent postoperative follow-up visits may be required. 
Obesity Medicine Physician Medicine
Gastrointestinal Unit, Department of Medicine
Division of Endocrinology, Department of Pediatrics
Massachusetts General Hospital/Harvard Medical School
FCS declares that she has acted as a consultant for Novo Nordisk. FCS is the author of an article cited in the topic.
Dr Fatima Cody Stanford would like to gratefully acknowledge Dr Abeezar Sarela and Dr Daniel M. Herron, previous contributors to this topic. AS has no competing interests. DMH has received educational grants from Ethicon Endosurgery and Covidien. DMH has acted as consultant for USGI Medical, Virtual Incision, and Hourglass Technology.
Group Health Center for Health Studies
DA declares that he has no competing interests.
Consultant in Bariatric and General Surgery
Chelsea and Westminster Hospital
EE has been sponsored by Ethicon UK in a fellowship grant and has received sponsorship to attend conferences. EE has received speaking fees from Nestle UK.
Internal Medicine and Pediatrics
Associate Medical Director
Chronic Disease Management
Ohio State University Hospitals
DPS declares that she has no competing interests.
Clinical Lecturer in Surgery
Imperial College London
HA declares that he has no competing interests.
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