Running a large longitudinal multi-center study to measure visceral fat and hepatic fat fraction present unique challenges. We scanned fat/water and ex vivo liver phantoms across all sites and over time to show consistency. SliceOmatic and ImageJ were used for quantification of visceral fat and LCModel for hepatic fat fraction. Visceral fat showed a good correlation with hepatic fat and demographics. The use of phantoms and careful design of the protocol can help address challenges of a longitudinal study and help maintain consistency across sites.