Background/Objectives: Insufficient dietary fiber intake contributes to gut microbiota dysbiosis, systemic inflammation, and the onset of obesity-related metabolic disorders. Agro-industrial by-products have emerged as sustainable sources to restore microbial and metabolic balance. This study aimed to evaluate the effects of a mango bagasse- and peel-based confectionery (MC) on gut microbiota composition, short-chain fatty acids (SCFAs), and hepatic gene expression in Wistar rats fed either a standard diet (STD) or a high-fat diet (HFD). Methods: Twenty-four rats were randomly assigned to four groups (STD, MC-STD, HFD, MC-HFD) and treated for 11 weeks. Eating behavior, body composition, microbiota composition, SCFAs, and hepatic transcriptomics were evaluated. Results: MC supplementation did not significantly alter weight gain or SCFA levels but shifted clustering patterns in principal component analysis, indicating a distinct dietary response. Microbiota analysis revealed a trend toward lower relative abundances of obesogenic species such as Phascolarctobacterium faecium and Ruminococcus torques, while Intestimonas butyriciproducens and Anaerostipes hadrus were modulated according to diet type. Transcriptomic profiling demonstrated consistent downregulation of lipid metabolism–related genes (Cyp4a14, Hmgcs1, Cyp51, Fads1), linked to PPAR signaling pathways. Conclusions: MC supplementation may beneficially modulate the gut–liver axis and highlights the nutritional potential of fruit by-products as functional ingredients to promote metabolic health under high-fat dietary conditions.

Dietary fiber and phenolic compounds are key bioactives in gastrointestinal and metabolic health; however, their compositional features and metabolic implications have rarely been studied as an integrated system within realistic food matrices. Mango bagasse confectionery previously demonstrated prebiotic potential, and its reformulation with extruded mango peel showed hepatoprotective effects linked to gut microbiota modulation. In this study, mango bagasse and peel confectionery (MBPC) was characterized and its metabolic impact was evaluated in vivo. Wistar rats were fed standard or high-fat diets with or without MBPC supplementation, followed by fecal fatty acid analysis. MBPC exhibited a high dietary fiber content for a confectionery product (25 g total fiber per 100 g), with monomeric profiles indicative of cell wall-derived polysaccharides and pectic components. The fiber fraction showed a low Mw (14.71 ± 0.02 kDa), suggesting a matrix favorable for fiber–phenolic interactions. Phenolic profiling revealed substantial concentrations of free (9.0 mg/mL) and bound (16.7 mg/mL) phenolic compounds. Fecal fatty acid profiles were diet-dependent, with palmitic acid showing the highest relative abundance, followed by stearic, oleic, and linoleic acids, associated with dietary fiber intake. This study elucidates the structural and metabolic relevance of dietary fiber–phenolic interactions within a formulated food matrix.