Racial/ethnic differences in risk factors for health, including 'thriftiness' in body fat accumulation are often evident before the age of 7, suggesting that the racial/ethnic differences in energy utilization and subsequent fat storage may be accounted for by genetic make-up, the environment (e.g. diet), or an interaction of the two. The physiologic or behavioral process(es) that cause(s) certain children to take a trajectory towards obesity while others accrue less fat is not known. However, the economic decision of fuel utilization is a physiologic trait enabling the body to choose between shuttling 'energy' towards accrual of a particular tissue (e.g. bone vs. fat) and this trait likely has a genetic component. This genetic component may be embedded in fat storage capacity evolved from gene by environment interactions that promote thrift, particularly conserved in some populations. Although genetic background plays a role, it not known whether there is a relationship between genetic background, known candidate genes or candidate pathways and environmental contributors (e.g. diet) that impact body composition trajectory. Of central importance to our understanding of early fat mass accumulation in health disparities are the mechanisms that lead to chronic disease progression.