Investigating the effect of bariatric surgery on lipid and glucose absorption via mathematical models

Obesity occurs as the excessive accumulation of the fat tissue in the body in comparison to other tissues. Obesity has become an important public health problem worldwide because it leads to various comorbidities such as type 2 diabetes (T2D), cardiovascular diseases (CVD) insulin resistance, hypertension, high cholesterol, and cancer. The majority of the people who are struggling with obesity can not succeed at losing weight by conventional methods such as diet and exercise. Moreover, subjects usually regain the weights they lose through these conventional methods in the future. The bariatric surgery, which is an effective method for treating patients with obesity, provides significant weight loss, and results in several metabolic ameliorations. In addition to that, studies show that bariatric surgery is more effective at sustaining the weight loss when compared to conventional methods. Roux-en-Y Gastric Baypass (RYGB) surgery is one of the most commonly performed bariatric surgery methods in the World. With this method, due to the reduced stomach volume, the amount of the consumed food is reduced and some of the nutrients are not absorbed. Therefore, RYGB surgery results in significant weight loss in morbidly obese patients, as well as improves diabetes, sleep apnea, and insulin resistance. In this thesis, the impact of the anatomical changes that take place after RYGB surgery on the lipid and glucose absorption is investigated. For this purpose, we developed physiologically based mathematical models of the gastrointestinal tract and utilized clinical data collected from patients that went through RYGB surgery at Amsterdam University Medical Center. The developed mathematical models are shown to be effective at understanding the impact of the surgery on lipid ang glucose absorption. Through mathematical modeling, physiological parameter values were estimated for pre- and post-surgical configurations and their differences were analyzed. This way some important metabolic changes that occur as a result of surgeries have been identified.