Dr Alexander MirasMADHAWI MOHAMMED OMAR ALDHWAYAN2022-06-062020-03-092022-06-0681307https://drepo.sdl.edu.sa/handle/20.500.14154/67753Background: Roux-en-Y gastric bypass (RYGB) surgery decreases hunger, increases satiety and changes food preferences. It is unclear which component of the RYGB is responsible for these changes. The duodenal jejunal bypass liner (DJBL) is used for the treatment of patients with obesity and type 2 diabetes and reproduces the exclusion of the proximal small intestine of the RYGB. The objective of this study was to employ a reductionist approach to determine whether the bypass of the proximal intestine is the component conferring the effects of RYGB on eating behaviour using the DJBL as a research tool. Aims: To investigate the effects of the DJBL versus standard medical care for patients with obesity and T2DM on: a) Total caloric intake and food preferences b) Sweet taste detection and intensity. c) Appetitive and consummatory reward value of sweet taste. e) Psychological aspects of eating behaviour. f) Fasting and postprandial concentrations of glucose, insulin, GLP-1, PYY. Methods: This thesis was part of a large randomised clinical trial comparing standard medical therapy with vs. without the DJBL for patients with obesity and type 2 diabetes. Forty-seven participants were involved in this nested study (27 DJBL group and 20 control group). Mechanistic visits were performed at baseline, ten days, six months, 12 months, and 24 months after intervention using direct and indirect assessments. 3 Results: 1. Both groups significantly reduced total caloric intake up to 12 months, then gradually started to increase through the second year. 2. There were no consistent changes in food preferences. 3. There were no significant changes within or between groups in the sensory or reward domain of sweet taste. 4. Both groups had improvements in the psychological aspects related to eating behaviour. 5. GLP-1 and PYY were significantly higher in the DJBL group at six months compared to the control group. 6. Late-phase glucose and insulin concentrations were significantly lower in the DJBL group compared to the control group. Conclusion: Weight loss was shown to be primarily due to caloric reduction with no superior benefit caused by the bypass of the proximal small bowel. The DJBL also resulted in a modest change in food preferences. No changes were observed in any of taste domains. There was a higher concentration of GLP-1 and PYY at six months, as well as lower glucose and insulin concentrations in the DJBL group. My findings suggest that the bypass of the proximal intestine in RYGB might not be the component of the surgery that underlies the reduction in energy intake and change in food preferences.205enThesis