High-fiber Diet on the Body and the Brain

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

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.

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