High-fiber Diet on the Body and the Brain

Study Overview
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Brief Summary
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The central research question aims to understand what drives individuals to make and maintain a vegan / vegetarian dietary decision, to investigate whether there are possible predictors that might influence such a decision and whether personality differences already exist or can only be measured after the change in diet. The investigators will examine the effects of a high-fiber diet on food wanting on a neural and on a behavioral level. The microbiome is suggested to mediate the expected changes in food wanting.

Official Title
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Interventional Study Comparing the Effect of a High-fiber Supplement Versus Placebo on the Body and the Brain

Conditions
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Diet Modification, Overweight

Intervention / Treatment
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* Dietary Supplement: inulin
* Dietary Supplement: maltodextrin


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: body-mass-index 25-30kg/m^2 females on contraception only Exclusion Criteria: current neurological or psychiatric illness daily consumption of more than 50 g of alcohol, more than 10 cigarettes or more than 6 cups of coffee use of antidepressants or other centrally acting drugs type 2 diabetes mellitus or other serious metabolic disorders MRI contraindication (e.g. cardiac pacemaker, drug pump, shunts) major untreated medical condition, including gastrointestinal organs, lungs, heart, cardiovascular system, liver and kidney) diet-related restrictions (food allergies, food intolerances, known nutrient deficiencies or a recent history of dieting or restrictive eating behaviour, including vegan, vegetarian diet) current pregnancy or lactation

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 45 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
Allocation: Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: Arm 1: inulin; minimum of 14 days wash-out; 14 days placebo Arm 2: 14 days placebo; minimum of 14 days wash-out; 14 days placebo
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: inulin<br> | Dietary Supplement: inulin<br>* prebiotic supplement<br>|
| Placebo Comparator: maltodextrin<br> | Dietary Supplement: maltodextrin<br>* placebo supplement<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| fMRI BOLD activity during food wanting |  | 14 days | 
| microbial alpha and beta diversity | The taxonomic structure of the microbial community will be determined using 16S rRNA gene sequencing. The reads from the sequencing data will be assigned to taxa by sequence similarity using puplic available data bases. Relative distribution of microbial taxa is then based on the number of reads assigned to each taxa. For the description of the the community the alpha diversity of each sample will be determined based on species richness, evenness of species distribution which is combined in the single value of the Shannon diversity index. Furthermore beta-diversity, how the microbial communities differ between sample, will be analysed by principal component analysis as well as non-metric multidimensional scaling. In addition, for each taxa significant difference between sample groups will be assessed by comparing the relative number of reads. | 14 days | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| fMRI BOLD activity memory performance |  | 14 days | 
| positive and negative affect | PANAS (Positive and Negative Affect Schedule); scores can range from 10 - 50, with higher (lower) scores representing higher (lower) levels of positive (negative) affect | 14 days | 
| mood | POMS (Profile of Mood States); four scales (Depression/Anxiety, Fatigue, Vigor, Anger), 35 items, 7 point scale, instruction How you have been feeling during the past 24 hours? | 14 days | 
| emotional health | BDI-II (Beck Depression Inventory); score minimum 0 to maximum 21 | 14 days | 
| well-being | WHO-5 (World Health Organization Well-Being Index); measures life quality and life contentment; score minimum 0 to maximum 5 with higher score representing higher life quality and life contentment | 14 days | 
| satiety | self-reported hunger scale; visual analogue scale; score minimum 0 to maximum 8 | 14 days | 
| serum lipid metabolism markers | total cholesterol, triglycerides, high density lipoprotein, low density lipoprotein | 14 days | 
| serum glucose metabolism markers | glucose, insulin | 14 days | 
| serum glucose metabolism markers | long-term glucose marker HbA1C | 14 days | 
| serum inflammatory markers | high sensitivity C-reactive protein, interleukin-6 | 14 days | 
| hunger hormones | leptin, ghrelin, Glucagon-like peptide-1 (GLP-1), peptide YY | 14 days | 
| serum microbial metabolic markers | short-chain fatty acids (SCFA), trimethylamine N-oxide (TMAO), bile acids | 14 days | 
| personality traits | BFMM (BIG FIVE Mine Marker); measures the Big Five personality traits as states; 5 subscales (neuroticism, extraversion, openness, agreeableness, conscientiousness); higher scores means being more extreme for a certain state | 14 days | 
| gastrointestinal health | GQLI-10 (Gastrointestinal Quality of Life Index); 10 items to measure quality of life regarding gastrointestinal symptoms; the higher the score the stronger the symptoms | 14 days | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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fiber, microbiome, food wanting, memory