Appetite regulation is a lifestyle intervention strategy to maintain health. The regulatory effects of dietary fiber (especially insoluble dietary fiber), as a crucial element of the nutritional composition, on appetite remain poorly understood. This study investigated modulatory effects of konjac fiber (KF, with high and low expansion) and konjac powder (KP) on chyme digestion, gastrointestinal hormones, intestinal microbiota, appetite genes in hypothalamus, GLP-1 receptor (GLP-1R) protein in various tissues of rats by dietary intervention. The results showed that highly-expanded konjac fiber (HKF) significantly delayed gastric emptying and inhibited hydrolysis of chyme. Konjac fiber (KF), especially HKF, and KP increased short-chain fatty acid (SCFA) content and plasma glucagon-like peptide-1 (GLP-1) levels. HKF upregulated the expression of GLP-1R protein in rat stomachs, nucleus tractus solitaries (NTS), and area postrema (AP) of rat brain, but down-regulated the expression of appetite gene AgRP/NPY in hypothalamus, thus, inhibiting appetite, reducing daily food intake and weight gain. Overall, this study reveals the mechanism through which expandable konjac fiber modulates appetite and chyme digestion in vivo by stomach-intestine-brain axis. Our findings provide an insight into the regulatory effects of insoluble dietary fiber on appetite and offered a valuable reference for the development of satiety-enhancing functional foods.