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Title: Modulation of food reward systems by fasting and ghrelin : human functional MRI studies
Author: Prechtl de Hernandez, Christina
ISNI:       0000 0004 2707 4755
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2011
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Background: To understand the pathophysiology of obesity, the role of hedonic eating needs to be considered. Neuroimaging research has suggested that activity in brain reward systems is modulated by the rewarding properties of food, nutritional state, and individual differences in eating behaviour. The interaction between these factors and the influence of gut hormones, such as the stomach-derived orexigenic hormone ghrelin, on these systems remains unclear. Methods: In the first study, 20 non-obese subjects were either fasted or ate a filling breakfast of their choice (fed). In the second study, 18 non-obese subjects were either fasted or given a fixed breakfast and received a subcutaneous saline or ghrelin injection. Subjects underwent functional MRI scanning while viewing and rating the appeal of food and object pictures and completed appetite and psychological questionnaires. Results: The first fMRI study showed that fasting increased activation to pictures of highcalorie over low-calorie foods in the ventral striatum, amygdala, anterior insula, medial and lateral orbitofrontal cortex (OFC). Fasting also biased the appeal towards high-calorie foods. Dietary restraint positively correlated with activation in executive systems when viewing high-calorie compared to low-calorie foods, but negatively correlated with activation in affective systems. Reward drive positively correlated with activation in the ventral striatum to high-calorie foods. In the second fMRI study activation to high-calorie foods in the insula and/or OFC when fasted and fed was shown to correlate with hunger and predict subsequent food intake. Administration of ghrelin was shown to mimic fasting to increase the appeal of high-calorie, especially sweet foods, and OFC activation to high-calorie foods. Conclusion: The results suggest an interaction between homeostatic and hedonic aspects of eating behaviour, with fasting and ghrelin biasing brain reward systems towards highcalorie foods.
Supervisor: Bell, Jimmy ; Frost, Gary ; Goldstone, Tony Sponsor: Medical Research Council ; European Union NuSISCO (Marie-Curie Fellowship) ; NIHR Biomedical Research Centre
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral