Focus on Fibre Study

Study Overview
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Brief Summary
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The investigators present a diet intervention study, to be conducted as a within-subject design, with all food and beverages provided, to allow ad libitum feeding to assess impact of diet change on appetite response. The diets will vary in fibre content and type. This study will allow assessment of the physiological impact of dietary fibre on markers of appetite control for body weight, measured from plasma gut hormones. The investigators propose to recruit participants with a poor diet quality (low habitual fibre intake) to additionally examine the time-course of adaptation of the gut microbiome (measured in faecal samples), whilst assessing the impact of added fibre on body weight and subjective appetite scores. This approach is to address the impact of dietary fibre in people living with obesity and food inequalities. The investigators will assess physiological bio-markers of appetite control and their contribution to the development of a gut ecosystem that promotes health. A subsequent period of return to a low fibre feeding will allow assessment of durability of response.

Official Title
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Healthy Diets for a Healthy Weight: Exploring Physiological Mechanisms Related to Dietary Fibre

Conditions
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Appetitive Behavior

Intervention / Treatment
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* Other: Phase 1 - Control
* Other: Phase 2 - High Fibre
* Other: Phase 3 - Low Fibre


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: healthy but overweight/obese (BMI 28-40kg/m2) males and females (post-menopausal, using the oral contraceptive pill or some form of hormonal contraceptive) low habitual fibre intake (<10g/day) Exclusion Criteria: Medication exclusion criteria: antibiotic use (within the past 3 months due to impact on gut microbiota) statins (current) aspirin or other NSAIDs or anti-coagulants (current) anti-depressants (current) smoking or vaping Medical exclusion criteria: Females who are planning to be pregnant, are pregnant or are breastfeeding Anyone with food allergies, self-reported food sensitivity or intolerance Anyone with coeliac disease or gluten intolerance Anyone taking medication which may affect their appetite Anyone with an eating disorder Anyone with diabetes Anyone with a gastrointestinal disorder, kidney disease, liver disease or gout Anyone suffering from a psychiatric disorder or any type of substance abuse Anyone suffering from unregulated thyroid disease Other exclusion criteria: Anyone following a vegetarian or vegan diet Anyone following a weight loss programme (that may be affecting lifestyle, physical activity & diet) Anyone with unsuitable veins for blood sampling Anyone who is unable to fluently speak, read and understand English Anyone who is unable to comply to an alcohol-free diet for 6 weeks

Ages Eligible for Study
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Minimum Age: 18 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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Design Details

Primary Purpose: Basic Science
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Control - High Fibre - Low Fibre (CTRL - HF - LF)<br>Phase 1 - CTRL: Control diet with moderate fibre consumption for 13days. Phase 2 - HF: ad libitum consumption of HF meals for 13days. Phase 3 - LF: ad libitum consumption of LF meals for 13days. | Other: Phase 1 - Control<br>* Control diet (30% Fat, 15% Protein, 55% Carbohydrate, Fibre rising from 10 to 16g/d). Fed to energy balance (1.5 x Resting Metabolic Rate, RMR).<br>* Other names: Phase 1 - CTRL;Other: Phase 2 - High Fibre<br>* High Fibre diet (30% Fat, 15% Protein, 55% Carbohydrate, 30g/day Fibre). Fed ad libitum, contains 20g/day pectin (split over breakfast, lunch and dinner) in drinks/yoghurts which will be compulsory to consume and 10g/day fibre coming from the diet provided.<br>* Other names: HF;Other: Phase 3 - Low Fibre<br>* Low Fibre diet (30% Fat, 15% Protein, 55% Carbohydrate, 10g/day Fibre). Fed ad libitum.<br>* Other names: LF;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in gut hormones to assess appetite response to dietary fibre | measured by acute and chronic changes in plasma ghrelin and peptide YY (PYY) | At baseline and end of each arm (study days 0, 14, 28 and 42) | 
| Change in subjective hunger to assess appetite response to dietary fibre | measured by acute and chronic changes in appetite using visual analogue scale questionnaires | At baseline and end of each arm (study days 0, 14, 28 and 42) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in gut metabolites (from faecal samples) in response to dietary fibre | measured by changes in faecal short chain fatty acids concentrations | At baseline and end of each arm (study days 0, 14, 28 and 42) | 
| Change in gut microbiome composition (from faecal samples) in response to dietary fibre | measured by changes in bacterial 16S ribosomal ribonucleic acid gene sequencing; 16S rRNA | At baseline and end of each arm (study days 0, 14, 28 and 42) | 
| Change in glycaemic control in response to dietary fibre | measured by acute and chronic changes in plasma glucose and insulin | At baseline and end of each arm (study days 0, 14, 28 and 42) | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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appetite control, fibre, gut microbiome, glycaemic control