<p>High-fat content causes meat emulsion gels to be more susceptible to free radical attack, inducing gel deterioration. As fat substitutes, water and soluble materials provide options for food manufacturers, but both ignore the filling effect of fat particles, which is not conducive to the formation of dense gels. Hence, it is essential to identify effective alternative particles. Insoluble dietary fiber (IDF) from agroindustrial waste has emerged as a promising candidate for fat replacement owing to its water/oil absorption, filling functions, and partial antioxidant properties. Recycling these IDFs can help address global issues, such as economic, resource, and health issues. However, the source selectivity, effectiveness, and filling mechanism of the crude extracted IDF require further analysis. This article systematically reviews the feasibility of IDF as a natural filler to replace fat in emulsified meat products and summarizes the sources and modification methods of IDF. Furthermore, the filling mechanisms of the IDF were discussed from both the inactive filler and active filler perspectives. IDF as an inactive filler enhances gel strength through matrix reinforcement, water/oil absorption, non-covalent interactions (ion bonding and hydrogen bonding), and covalent interactions (disulfide bonding and amide bonding). Active IDF mainly alleviates oxidative damage through covalent binding between the residual water/lipid-soluble active ingredients and proteins. Finally, the challenges and solutions faced by IDF in the industrial application of emulsified meat products are summarized. Future research should focus on decoding the molecular binding sites between IDF and meat proteins and establishing a full-chain standard system for IDF production and application.</p> Graphical Abstract <p></p>