¹Biology Department, Faculty of Mathematics and Natural Sciences, Andalas University, Padang, Indone DOI : 10.29228/jrp.818 Yam bean (Pachyrhizus erosus L.) is a prominent medicinal plant exerting various health benefits. However, it remains unknown whether yam bean fiber (YB) is also capable of counteracting the deleterious effects of a high-fat diet (HFD) on the small intestine. This present study aimed to investigate the effect of YB supplementation on the glucagonlike peptide 1 (GLP-1) expression, oxidative stress, and histopathological alterations of the small intestine in mice fed an HFD. Twenty-seven mice were assigned equally into three different diet treatment groups: normal diet (ND), HFD, and HFD supplemented with 10% of YB (HFD + YB). After eight weeks, mRNA expression of GLP-1, malondialdehyde (MDA) levels, catalase (CAT) activity in the small intestinal tissue were determined, and the anatomical and histopathological alterations of the intestine were investigated. The results demonstrated that YB supplementation was effective in precluding HFD-indued reduction of GLP-1 mRNA expression in the small intestine. YBF also prevented MDA elevation while ameliorating CAT activity. Furthermore, YBF exerted an ameliorative effect against HFD-induced morphological and histological alterations of the small intestine, particularly in intestinal length, index, and the number of inflammatory cells in the mucosal layer. This study revealed that YB supplementation could effectively prevent the impairment of GLP-1 expression and oxidative stress while ameliorating the histopathological alterations of the small intestine caused by HFD. Hence, YB could be formulated as a supplement to improve the gastrointestinal structure and functions against HFD. Keywords : catalase activity; GLP-1, inflammatory cells; malondialdehyde; oxidative stress, small intestine, yam bean