Guidelines from the American Academy of Pediatrics’ new clinical report propose that parents and pediatricians work together to improve children’s diets and activity levels at home, in order to help curb childhood obesity rates.

“I think the good that can be done in terms of prevention and early intervention especially down to the young ages … is tremendous compared to the degree of difficulty everyone has when the family, the child and the practitioner are trying hard to work on a child who already has developed obesity,” said report co-author and AAP President Sandra G. Hassink.

The new report, “The Role of the Pediatrician in Primary Prevention of Obesity,” updates the AAP’s 2003 policy statement, and appears in the journal Pediatrics. It states that childhood obesity has doubled and even tripled for some certain age groups, and that it’s the most prevalent chronic health condition for children.

According to the Centers for Disease Control and Prevention, more than one-third of American children and teens are overweight or obese. This health crisis is the result of several factors. Nearly half of all middle and high schools in the U.S. allow advertising for less healthy foods, which influences students’ ability to make healthy food choices. Between 1977 and 1996, hamburger portion size increased 23%, soft drink portion sizes by 52%, and snack portion sizes by 60%, according to a study by the University of North Carolina at Chapel Hill. In addition to several other factors, this combination of choosing less healthy food in larger portions is causing childhood obesity.

In order to combat the problem, AAP encourages parents to help improve childrens’ eating habits and levels of activity at home, emphasizing family-based strategies to promote healthier lifestyles.

“Once obesity is established, it’s very hard to treat,” said Dr. Stephen Daniels, chairman of the AAP nutrition committee and the University of Colorado School of Medicine’s chair of pediatrics.

Because treating obesity takes so much time and effort, the report emphasizes prevention.

According to Daniels, “The home environment has a big influence on what kids eat and how active they are.”