Mice studies suggest that gut microbiome friendly oat and barley fiber containing beta-glucan can increase butyrate in the gut. "Butyrate induces the release of glucagon-like peptide-1 (GLP-1), which is the natural protein that synthetic drugs like Ozempic mimic to stimulate insulin release." This lead to weight loss in the mice.
The research has not been replicated on humans yet but you can readily buy beta-glucan and butyrate suppliments.
https://www.sciencealert.com/one-type-of-fiber-may-have-weight-loss-benefits-similar-to-ozempic