Neurocognition and food cue-related brain reactivity after fiber supplementation within a high-protein, plant-based diet in individuals with overweight and prediabetes: A randomized-controlled trial (the DISTAL-study)

BACKGROUND: The increasing prevalence of obesity and related diseases, such as type 2 diabetes mellitus (T2DM) and neurocognitive dysfunction, warrants sustainable and effective strategies for treatment and prevention. A healthy diet, containing dietary fibers that are fermented by the gut microbiome, produces short-chain fatty acids, among other metabolites, known to alleviate insulin resistance. SCFA also may protect against neurocognitive decline and increase satiety through food-reward-related pathways of the gut-brain axis, thereby contributing to sustainable dietary habits and counteracting obesity and -related diseases. We therefore studied the effects of dietary fibers in the context of a high-protein, partially plant-based diet on neurocognitive functioning and food-reward related brain activity. METHODS: This 12-week RCT compared a potato fiber and sugar beet pectin supplement to an isocaloric placebo (maltodextrin), both within a high-protein (±45% plant-based) diet. We investigated the effects on food-reward-related brain activity using functional magnetic resonance imaging (fMRI) with visual food stimuli, comprising high-calorie, low-calorie, and non-food items. Neurocognitive performance was tested with the Cambridge Neurocognitive Test Automated Battery (CANTAB). Furthermore, satiety hormones, stress, and general well-being were assessed, and associations with cardiometabolic markers were explored. RESULTS: Overall, there was a trend towards an increased amygdala BOLD response over time in the fiber group compared to placebo, independent of visual stimuli conditions. The change in amygdala activity was positively associated with increased colonic permeability in both groups. After the intervention, both groups showed improvements in psychomotor speed, visual memory, and learning abilities, and reported less subjective hunger after 12 weeks on a high-protein, partially plant-based diet. General well-being, stress, and satiety hormone concentrations remained unchanged. CONCLUSION: Twelve weeks of fiber supplementation did not change brain activity induced by visual food cues in reward-related brain regions. However, the high-protein, partially plant-based diet seemed to provide neurocognitive benefits, improving psychomotor speed and memory, and decrease perceived hunger.