Background
Family-based approaches have been reported to be effective in improving overweight or obesity in children.

Objectives
To investigate the relationship of changes in BMI and metabolic parameters between adults with overweight and obesity and their children during a weight-maintenance family based dietary intervention.

Methods
In a multicenter Randomized Controlled Trial, families with at least one overweight or obese parent and one healthy child aged between 5-18 years, of which the parents completed an 8-week weight loss phase succesfully, were randomized into five different dietary intervention groups to achieve weight maintenance for 6-months. Anthropometric parameters and body composition were measured and blood samples were collected before and after the dietary intervention.  Data were analyzed using Pearson correlation coefficient analyses and multiple linear regression analysis adjusted for diet group, center, child’s sex and age. 

Results
A positive association was found between the change in BMI of the mother and change in BMI-for-age Z-scores of the 1^st and 2^nd child (std  = 0.248, P = 0.000; std  = 0.326, P = 0.000, respectively). The change in BMI of the father was only significantly associated with the change in BMI-for-age Z-scores of the 1^st child (std  = 0.186, P = 0.031). No consistent pattern of associations between parents and children was found for HOMA-IR, fasting glucose and fasting insulin.

Conclusion
Better weight maintenance in parents after a weight loss intervention is associated with less increase in BMI z-score in their children, which were included in the dietary weight maintenance intervention. This study supports the inclusion of parents into family-based dietary approaches for weight management of their children regardless of the child’s weight status in 8 different countries throughout Europe.