Degree Name

Doctor of Philosophy


School of Medical, Indigenous and Health Sciences


Obesity has been recognised as a chronic relapsing and complex condition. The tendency to maintain a physiological set point makes it challenging to achieve and maintain a significant weight loss in those with a Body Mass Index (BMI) of > 30 kg/m2 [1]. The medical treatment options for obesity are currently limited and costly, with little long-term data on weight loss and potential side effects. Bariatric surgery is an effective treatment of choice in treating obesity. It results in the resolution or improvement of obesity-related co-morbidities such as diabetes mellitus, hypertension, sleep apnoea, abnormal lipids, non-alcoholic fatty liver disease, and improves quality of life [2-5]. In clinical settings, most patients who seek bariatric surgery have experienced the cycles of dieting, achieving weight loss, and the disappointment of subsequent weight regain. Patients seek bariatric surgery to achieve significant weight loss, better satiety and hunger control. This subsequently results in improved medical and mental health, mobility and, consequently, better quality of life.

All bariatric procedures change the anatomy and physiology of the gastrointestinal system. Changes in food preferences, taste, diet tolerance and nutritional deficiencies have also been reported in various degrees following these procedures [6-8]. These side effects collectively impact the ingestion, digestion and absorption of nutrients, hence the need for specific and long-term medical nutrition therapy in this cohort [5]. The focus has traditionally been on the short-term reduction of diet quantity (the amount of food consumed) and the associated reduced energy (kilojoules/calories) intake. However, long-term clinical issues such as sustained diet quality, specific nutritional deficiencies, long-term follow-up, and loss to follow-up have been difficult to explore. Following surgery, the physiological adaptation of the gastrointestinal system and hence the ability to consume more food are likely to impact lifestyle and diet quality choices, possibly leading to weight regain. This also needs attention. Finally, emerging new procedures, such as One Anastomosis Gastric Bypass – Mini Gastric Bypass (OAGB - MGB), can be associated with more gastrointestinal symptoms that may impact nutritional status and quality of life. However, this area has not been extensively studied.

FoR codes (2008)




Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.