Polyether antibiotics inhibit adipogenesis. Dose-dependent (1, 5, 10, 50, 100, and 200 nM) inhibition of OP9 stromal cells differentiation into adipocytes by monensin, salinomycin and narasin, compared to TNFα, a cytokine and potent inhibitor of adipogenesis, as well as rosiglitazone (Rosi) an inducer of preadipocyte differentiation into adipocyte. Differentiated adipocytes were stained with Nile Red. Vehicle treated OP9 cells including dimethylsulfoxide (DMSO) and methanol (MeOH) served as controls. Representative micrographs of one of the experiments, which were performed for at least three or more times, are shown.