Unpublished data collected in older participants undergoing a 6-month weight loss intervention indicate that it i possible to generate a clinically meaningful 400-meter walk gait speed difference of at least 0.05 m/s, with a common group standard deviation of 0.19 m/s and a correlation of 0.85 between baseline and 6-month measures. An analysis of covariance (ANCOVA) analytic approach will be used to fit the randomization effect and baseline gait speed, then 53 subjects completing the intervention per group will yield 80% power using a two-sided alternative hypothesis at the 0.05 level of significance. Assuming a conservative drop-out rate of 15%, there is a 124 participants (n=62/group) enrollment goal.