Responses to Appetite and Taste in the Brain Circuits That Control Eating Behaviour

Study Overview
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Brief Summary
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The aim of this study is to gain insight into brain structure and the neural networks that control taste and eating behaviour in patients with severe obesity undergoing a primary sleeve gastrectomy (SG) or a lifestyle intervention for weight loss compared with normal weight individuals, using functional magnetic resonance imaging (fMRI).

Detailed Description
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This is an observational study aiming to gain insight into brain structure and the neural networks that control taste and eating behaviour in patients with severe obesity undergoing a primary sleeve gastrectomy (SG) or a lifestyle intervention for weight loss compared with normal weight individuals using functional magnetic resonance imaging (fMRI). Drops of liquid foods and a control solution will be delivered to the participants' mouth during fMRI scanning. Body weight, gut hormones from serial blood samples, appetite scores and taste will be assessed at each study visit.

Official Title
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Responses to Appetite and Taste in the Brain Circuits That Control Eating Behaviour: An fMRI Study Evaluating Brain Structure, Connectivity and Responses to Taste Across Different Body Weight Categories and in Response to Weight Loss

Conditions
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Obesity

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Female and male adults aged 18-50 years. Right-handed. No MRI contra-indications. Weight stable at time of recruitment, defined as less than 5% variation in body weight over the preceding 3 months. Proficient in written and spoken English. Able to comply with study protocol. Willing and able to provide written informed consent. Participants must be registered with a general practitioner (GP). Willing for their treating consultant or their GP and the study team to be informed in the event of an incidental abnormal finding being detected by the investigations or assessments that form part of this study. Able to lie flat for 1 hour. Group-specific inclusion criteria: SG group: BMI of 35-50 kg/m2 Planned to undergo primary SG surgery and fulfilling eligibility criteria for bariatric surgery. Lifestyle intervention group: BMI of 35-50 kg/m2 Willing to undergo a lifestyle intervention programme with a view to achieving approximately 10% weight loss. Normal weight group: BMI 18.5-24.9 kg/m2 Exclusion Criteria: Body weight greater than 130kg (due to weight limit of MRI Scanner). Contraindications specific to MRI scanning: metallic implants (cardiac pacemakers, aneurysm clips, permanent eye lining, cochlear implants or anyone who has been exposed to metallic flakes or splinters). Type 1 and type 2 diabetes (in view of altered circulated gut hormone profiles and gustatory function). Menopause (in view of findings that the menopause affects gustatory function). Smoking (in view of the fact that smoking affects salivary gut hormones and gustatory function). Vitamin B12 or zinc deficiency (in view of deficiencies affecting gustatory function). Untreated severe depression. Eating disorders including bulimia and self-induced vomiting. Neurological or psychiatric conditions. Acute illness or chronic conditions that may impact upon gustatory and olfactory function. Acute illness or chronic conditions that may impact upon post-operative weight loss. Known or suspected history of HIV, Hepatitis B or C or other blood-borne diseases (in view of safety regulations regarding exposure to blood products) Pregnancy or lactation.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 50 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Sleeve Gastrectomy (SG)<br>25 participants, male and female, aged 18-50 years, body mass index (BMI) 35-50 kg/m2, due to undergo primary SG | |
| Lifestyle Intervention<br>25 participants, male and female, aged 18-50 years, BMI 35-50 kg/m2 | |
| Normal Weight<br>25 participants, aged 18-50 years BMI 18.5-24.9 kg/m2, age and gender matched to group with severe obesity | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| BOLD signal change after SG | To determine the effect of SG, at 10% weight loss, upon whole-brain neural response to taste, in the fed and fasted state, detected through blood-oxygen-level dependent (BOLD) signal, in patients with severe obesity. | approximately 6 weeks | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| BOLD signal change after lifestyle intervention | The effect of 10% weight loss in patients with severe obesity induced by a lifestyle intervention on BOLD signal to taste in the fed and fasted state and compared to SG. | average of 12 weeks | 
| BOLD signal in response to taste in severe obesity compared to normal weight | Brain responses, as BOLD signal, to taste in the fed and fasted state in severe obesity compared to normal weight | baseline | 
| BOLD signal change post-SG | Whole brain neural response in BOLD signal to taste, in the fed and fasted state, 6 months following SG versus normal weight | 6 months | 
| Correlation of taste responses and gut hormones | The relationship between the neural correlates of taste and levels of circulating gut hormones in severe obesity compared to normal weight | baseline | 
| Correlation of taste responses and gut hormones | The relationship between the neural correlates of taste and levels of circulating gut hormones after 10% weight loss by SG compared to lifestyle intervention | approximately 6 weeks for SG group and approximately 12 weeks for lifestyle intervention group | 
| Correlation of taste responses and gut hormones | The relationship between the neural correlates of taste and circulating gut hormone levels | 6 months post-SG compared to baseline | 
| Correlation of taste responses and gut hormones | The relationship between the neural correlates of taste and levels of circulating gut hormones post-SG compared to normal weight | 6 months | 
| Brain structure | Comparison of brain structure in severe obesity and normal weight | Baseline | 
| Brain structure 6 months following SG | Comparison of brain structure 6 months following SG to baseline | 6 months | 
| Brain structure after 10% weight loss | Comparison of brain structure following 10% weight loss induced by SG versus lifestyle intervention | approximately 6 weeks for SG group and approximately 12 weeks for lifestyle intervention group | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Obesity, appetite, taste, fMRI