I don't doubt it at all. Kids looks like their parents. Parents that are tall and skinny have kids that are tall and skinny. Parents that are short and round have kids that are short and round. Families in which one parent is tall and skinny and one parent that is short and round tend to have kids that take after one parent or the other. Those kids usually have all the characteristics of the parent they favor - bone structure, facial features, hair color etc. Especially when younger, all family members usually eat pretty much the same way and have the same activity habits. Yet early on you can tell which parent the child will look like. It is doubtful that kids are choosing to eat poorly and skip exercise by the time they are 3 or 4 years old.