First, we hypothesize that participants who have a predominantly Prevotella enterotype (inferred by a high Prevotella/Bacteroides-ratio) will lose more body weight after AX supplementation compared to participants with a predominantly Bacteroides enterotype (inferred by a low Prevotella/Bacteroides-ratio). Specifically, we hypothesize that weight loss and P/B-ratio will be positively correlated in the AX supplementation-group whereas there will be no such correlation in the control-group. Consequently, we hypothesize that participants with the Bacteroides enterotype - and the lowest P/B-ratio - will have no benefit after AX supplementation while the weight loss effect of the AX supplementation will increase with increasing P/B-ratio.~Second, we hypothesize that the ability to digest starch in the upper gastrointestinal tract - evaluated by salivary alpha amylase gene (AMY1) copy number - will influence the interactions among AX intake, P/B ratio, and body weight change. Specifically, we hypothesize that there will be an association between body weight change and P/B ratio among subjects with a low AMY1 copy number, but not among the ones with a high AMY1 copy number, when consuming AX.
The overall aim of this 12-week randomized controlled trial is to investigate if a dietary fiber supplement rich in arabinoxylans (AX) affects weight loss success differently according to baseline gut microbiota composition in subjects who have overweight or obesity.~105 participants will be randomized in a 2:1 ratio to receive 15 g/day of AX or placebo.