Available data suggest that if energy expenditure (EE) is involved in the etiology of obesity, the component of interest is activity-related EE (AEE). However, most prior studies examining the role of EE did not ensure metabolically stable conditions, include controls, or distinguish subjects according to ethnicity or predisposition to obesity. This study proposes to longitudinally follow current participants in another study ("Energy expenditure in Post-obese black and white women") for the next 5 years. 31P magnetic resonance spectroscopy is being used to access the ATP cost of force production associated with a controlled exercise task. Currently, we are ending the 1st year of acquiring data on this longitudinal follow-up project and are in the initial stages of compiling the first set of data. At this time, we have no data to report.