Childhood obesity rates have tripled in the last 30 years, with as many as 50% of children in the US being obese or overweight. High-intensity comprehensive behavioral family lifestyle intervention (CBFLI) programs have been shown to be among the most effective interventions for weight loss in children. However, these programs are time- and resource-intensive with high rates of recidivism. Personal activity trackers (PAT) provide objectively measured physical activity data and are more reliable than self-report. These devices can also have a motivational impact. The investigators intend to study the effects of these devices and their data on behavior change and weight loss for both parents and children enrolled in a CBFLI program. The investigators will objectively measure the level of activity of both members of the parent-child dyad, explore the relationship between parent-child activity levels and its effect on each other, as well as on overall weight loss or weight maintenance.