Efficacy of Parent-Child Dieting Plans Incorporating Medifast Meal Replacements for Weight Loss

Weight Loss Phase: This phase will take place between week 0 and week 26 (6 months). Participants will be randomly assigned to one of two weight loss treatment groups: 1. Medifast meal replacement diet group (3 supplements per day) plus food-based diet 2. Reference diet group (Food Guide Pyramid-based diet) Participants will be further randomly assigned to one of two parent-child approaches: 1. Dieting child with one dieting parent 2. Dieting child without dieting parent Although it is encouraged to have both parents involved in the child's care, only one parent will be permitted to be dieting as a part of the study along with the child so that we can more cleanly assess the effects of a parent dieting without confounding effects of some families having two parents dieting. Both groups will attend separate biweekly educational lessons during the weight loss phase (same curriculum and teacher). Data collection visits will occur at baseline, week 12, and transition. There are a total of 31 visits for a child participating in this study, and 30.for a parent participating by dieting with their child. Transition Phase: Transition to a maintenance diet will be individually timed by participant attainment of goal "healthy" weight (BMI≤ 25) or week 26, whichever comes first. Maintenance Phase: This phase will occur after completion of weight loss or between weeks 27 and 78 (12 months). Groups will attend separate educational lessons (same curriculum and teacher) once every 4 weeks. The Medifast group will reduce supplements to 2 per day with a larger portion of calories from whole foods. The reference diet group will remain on a food-based (no supplements) maintenance diet for the entire 52+ week maintenance period. Data collection visits will occur at weeks 26 and 52.