Synergic effect of diet and polysaccharide-based complex administration in the treatment of children and adolescents with metabolically unhealthy obesity: the Polymets Study

Purpose: The primary aim of the Polymets Study is to evaluate the effect on gut microbiota composition of a polysaccharide-based complex administration combined with dietary and lifestyle interventions in a group of children and adolescents with metabolically unhealthy obesity (MUO). Methods: In this clinical trial, children and adolescents (8–14 years) with obesity (defined as body mass index > + 2 standard deviation score [BMI SDS] according to World Health Organization) and cardio-metabolic alteration (hypertriglyceridemia, hypertension, hypo-HDL cholesterol, altered glucose metabolism) were enrolled. Participants received from baseline (T0) to 4 months (T1) combined polysaccharide-based complex administration (5 g/day mixture of soluble and insoluble fibres) and Mediterranean diet intervention; from 4 to 8 months (T2) they underwent dietary intervention alone. At T0, T1 and T2 gut microbiota analysis, body composition assessment, blood tests and Mediterranean diet adherence (KIDMED score) were assessed. Results: Overall, 31 children were enrolled (10.9 ± 1.6 years, F/M 8/23). BMI SDS significantly decreased at each timepoint (p < 0.001), whilst fat mass% significantly decreased only at T1 (p = 0.035), vs T0. The Principal Component Analysis showed a trend of reduced dispersion at the phylum taxonomic level at T1, having Firmicutes, Bacteroidota and Proteobacteria as major contributors to the variance. At T1, there was an enrichment in Barnesiellaceae family, Erysipelotrichaceae_UCG-003 and Parabacteroides genera (p < 0.05), vs. T0. At T2 Oscillospiraceae_unclassified and Clostridia_unclassified increased significantly, whereas Erysipelotrichaceae_UCG − 003 and Escherichia_Shigella decreased significantly (p < 0.05), vs T1. Conclusion: Polysaccharide-based complex intervention synergistically contributes for enrichment in microbial marker of metabolic health and body adiposity reduction, while the subsequent solo-diet phase triggers expansion of butyrate-producing lineages and overall reduction of pathogenic taxa.