OBJECTIVES. The intent of this study was to evaluate whether small changes in diet and physical activity, as promoted by the America on the Move initiative, could prevent excessive weight gain in overweight children. METHODS. In this family-intervention study, the America on the Move small-changes approach for weight-gain prevention was evaluated in families with at least 1 child (7-14 years old) who was overweight or at risk for overweight. These children were the primary target of the intervention, and parents were the secondary target. Families were randomly assigned to either the America on the Move group (n = 100) or the self-monitor-only group (n = 92). Families who were assigned to the America on the Move group were asked to make 2 small lifestyle changes: (1) to walk an additional 2000 steps per day above baseline as measured by pedometers and (2) to eliminate 420 kJ/day (100 kcal/day) from their typical diet by replacing dietary sugar with a noncaloric sweetener. Families who were assigned to the self-monitor group were asked to use pedometers to record physical activity but were not asked to change their diet or physical activity level. RESULTS. During a 6-month period, both groups of children showed significant decreases in BMI for age. However, the America on the Move group compared with the self-monitor group had a significantly higher percentage of target children who maintained or reduced their BMI for age and, consistently, a significantly lower percentage who increased their BMI for age. There was no significant weight gain during the 6-month intervention in parents of either group. CONCLUSIONS. The small-changes approach advocated by America on the Move could be useful for addressing childhood obesity by preventing excess weight gain in families. Copyright © 2007 by the American Academy of Pediatrics.