Open Access
Feature Article

Bariatric surgery: positive and negative effects

Eddy J. Tabet, Ian D. Caterson, Tania P. Markovic


Dr Tabet is a Staff Specialist in the Department of Endocrinology at Royal Prince Alfred Hospital; and Clinical Associate Lecturer at The University of Sydney, Sydney. Professor Caterson is the Boden Professor of Human Nutrition and Director of The Boden Collaboration for Obesity, Nutrition, Exercise & Eating Disorders at The University of Sydney, Sydney; and an Endocrinologist at Royal Prince Alfred Hospital, Sydney. Dr Markovic is Director of Metabolism and Obesity Services at Royal Prince Alfred Hospital, Sydney; and Clinical Associate Professor, Boden Collaboration for Obesity, Nutrition, Exercise & Eating Disorders at The University of Sydney, Sydney, NSW.


Bariatric surgery is recognised as a legitimate treatment for obesity. Knowledge of its key long-term outcomes, such as durability of weight loss, remission of obesity-related comorbidities and surgical complications, has grown exponentially in recent years. Further insights into the physiological mechanisms underlying outcomes will drive more effective and less invasive techniques that can be individualised to a patient’s needs.

Key Points

  • Weight loss surgery now has long-term data supporting its efficacy and safety in the treatment of obesity.
  • Bariatric surgery produces sustained weight loss, leading to remission of type 2 diabetes, reduction in mortality and improvement in many cardiac risk factors.
  • Physicians should be familiar with the acute and chronic complications of the widely performed bariatric procedures.
  • Postoperative nutritional status and psychological wellbeing need to be monitored carefully in patients who undergo bariatric surgery.

Obesity increases the risk of many severe medical conditions ranging from metabolic disorders (type 2 diabetes, nonalcoholic steatohepatitis, cardiovascular disease), malignancies (colorectal, breast, uterine, oesophageal, renal and pancreatic), hypoventilation and respiratory failure, musculoskeletal disorders, dementia and depression. Importantly, it is independently associated with a reduced life expectancy. Obesity is a major health issue worldwide and in Australia it affects 31% of the adult population and 8% of children and adolescents.1 Despite clinical advances in our understanding of energy balance regulation, effective therapeutic outcomes elude many obese and overweight patients. The customary approach of recommending improvement to diet and exercise patterns does not produce sustained weight loss for most individuals. Newer pharmacological therapies have relatively limited efficacy and are costly, and can be poorly tolerated because of side effects.


A paradigm shift has seen bariatric surgery legitimised as an effective treatment of obesity, and the evidence for its efficacy and safety has grown exponentially. Results from randomised controlled trials have demonstrated clear superiority for bariatric surgery over nonsurgical strategies, at least for short-term outcomes such as remission of type 2 diabetes. Evidence of long-term outcomes is derived largely from observational studies. Ongoing challenges include the identification of eligible patients for bariatric surgery and selection of the most appropriate procedure for each individual and ensuring equitable access to this treatment modality for those most in need.