Althubeati, Sarah
(2024)
Regulation of Food Intake in Adults with and without Obesity: The Role of the Gastrointestinal Tract and Gut-Brain Axis.
PhD thesis, University of Nottingham.
Abstract
Obesity is a complex global health issue affecting a significant portion of the population. In the UK, it is estimated that approximately 1 in 4 adults and 1 in 5 children aged 10 to 11 years are living with obesity. Impairment in food intake regulation, including hunger and satiety sensations, are key factors contributing to overeating and weight gain, particularly in individuals with obesity. While various mechanisms may explain these alterations, such as altered appetite and satiety regulators, accelerated gastric emptying (GE), and heightened brain responses to food cues and reward, it remains inconclusive whether these mechanisms are altered in people living with obesity compared to normalweight (NW) adults.
There are various approaches to studying food regulation, each offering unique insights into the complex mechanisms that control appetite, satiety, and food intake. Non-invasive imaging, particularly magnetic resonance imaging (MRI), provides a powerful tool for investigating the physiological mechanisms underlaying the regulation of food intake. The work in this PhD thesis aims to combine physiological measurements obtained by using MRI with behavioural assessments (i.e., subjective satiety rating), to provide a more comprehensive understanding of appetite control in NW adults and alterations associated with obesity. The work in this thesis included a functional neuroimaging metaanalysis, and three eating behaviour intervention studies, two of which used MRI techniques.
A functional neuroimaging meta-analysis was performed to identify brain areas associated with changes in appetite and satiety regulators in NW and Obese adults. The caudate nucleus and hypothalamus were identified as key areas associated with satiety regulators in NW participants. However, conclusive findings for Obese participants were limited due to the small number of studies conducted in this area.
An MRI study was conducted to investigate the effect of a standard meal on gastrointestinal (GI) responses. The study found that GI responses including gastric content volume (GCV), GE rate, small bowel water content (SBWC), and superior mesenteric artery (SMA) blood flow, and appetite and satiety regulators were not significantly altered by obesity following the meal. However, Obese participants showed lower satiety subjective rating, and higher insulin and triglyceride levels compared to NW participants.
Different macronutrients play distinct roles in influencing feelings of fullness and satiety, and their impact on the satiety sensation can be a valuable strategy for weight loss. In a pilot MRI study combining gut and brain imaging, responses to a high-fat (HF) emulsion drink and a carbohydrate drink that is matched in caloric content, volume, and viscosity were assessed in NW and Obese participants. Data collection in this study was significantly impacted by the COVID pandemic; therefore, findings from this work are focused on GI responses. The results suggest that the HF drink might induce higher GCV, SBWC, SMA blood flow, and subjective satiety ratings when compared to an iso-caloric, and iso-viscous high carbohydrate drink (HC) in both NW and Obese.
The final study investigated the satiating effect of acute high protein consumption compared to high carbohydrate in NW and Obese participants using ad libitum meal intake and subjective satiety ratings. This study found no significant differences in ad libitum energy intake, subjective satiety, or energy intake between the drinks in either NW or Obese participants.
This research integrated different approaches to measuring the regulation of food intake and alterations in obesity. This holistic approach facilitates a comprehension understanding of the mechanisms governing food regulation, including the impact of macronutrient composition, hormonal influences, gastrointestinal responses, neural signalling, and eating behaviours. While the studies in the thesis did not reveal significant differences in certain aspects of appetite regulation between NW and Obese, including macronutrient compositions, they did highlight several areas requiring further investigations. The complicated nature of obesity and appetite regulation necessitates continued research to better understand these complex mechanisms and inform strategies for obesity management and prevention.
| Item Type: |
Thesis (University of Nottingham only)
(PhD)
|
| Supervisors: |
Salter, Andrew
Eldeghaidy, Sally
Lobo, Dileep N
Avery, Amanda |
| Keywords: |
obesity, food regulation, appetite, satiety, food intake, gastrintestinal tract |
| Subjects: |
Q Science > QP Physiology > QP1 Physiology (General) including influence of the environment
R Medicine > RC Internal medicine > RC 321 Neuroscience. Biological psychiatry. Neuropsychiatry |
| Faculties/Schools: |
UK Campuses > Faculty of Science > School of Biosciences |
| Item ID: |
77921 |
| Depositing User: |
Althubeati, Sarah
|
| Date Deposited: |
23 Jul 2024 04:40 |
| Last Modified: |
23 Jul 2024 04:40 |
| URI: |
https://eprints.nottingham.ac.uk/id/eprint/77921 |
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