Study authors Marissa Stroo and Dr. Truls Ostbye of Duke Medicine in Durham, N.C., and colleagues studied data from 190 kids, ages 2-5, whose mothers were overweight or obese. They collected information on the children's food intake over the past week, with foods rated as junk food or healthy food.
To gauge their levels of physical activity, the children wore accelerometers for a week, which measured moderate to vigorous physical activity as well as sedentary time.
Mothers reported family ideas about eating and activity, whether the parents role-modeled good eating and activity and what the kids ate during the week.
Stroo said when the parents did better, the kids did better.
For example, limiting access to junk food at home and parental policies supporting family meals increased the amount of healthy foods kids ate. Overall, the home environment had more influence on the children's dietary habits than on their physical activity levels.
The findings remind parents their children are watching and learning from observing their behaviors, both good and bad.
"It's hard for parents to change their behaviors, but not only is this important for you and your own health; it is also important for your children because you are a role model for them," Stroo said in a statement. "This might be common sense, but now we have some evidence to support this."
The study was published in the International Journal of Obesity.