Childhood obesity rates in America have tripled over the last 30 years, and a 2008 survey revealed that more than one third of children and adolescents in the United States were overweight or obese. Causes for these alarming numbers include such obvious factors as overeating and insufficient exercise, but two new culprits are also being examined for exacerbating the problem.

An explosion in the use of high fructose corn syrup among food manufacturers has been linked to the rise in obesity in both children and adults. The sweetener is present in large quantities in soft drinks, jam and many other processed foods. A recent article from the University of Colorado School of Medicine indicated that the metabolism of fructose can cause fatty liver, obesity, and insulin resistance. These conditions lead to the development of Type 2 diabetes, another disease on the rise among children.

Phthalates, which are chemicals commonly used in plastics, are also associated with the increase in childhood obesity. These chemicals are present in many household products and even some pacifiers. A study presented at this year’s annual meeting of The Endocrine Society in Houston indicated a significant correlation between phthalates and obesity.

The most common factors that contribute to childhood obesity are the ways in which kids are fed and the amount of television they watch. In both instances, parents can play a significant role in shaping healthy habits. Mothers should breast feed for as long as possible, ideally 6 to 12 months, and introduce solid foods between 4 and 6 months. Parents should ensure that their children eat a variety of fruits and vegetables and drink ample water. As kids often ask for the foods they see on television, it’s important to set limits there. Heading outdoors and becoming an active family boosts health for everyone.

Public schools can do much to reduce childhood obesity rates as well. In Wisconsin, a school superintendent recently directed all local schools to spotlight a large, attractive bowl of fruit at the beginning of the cafeteria line. Children in those schools chose almost twice as much whole fruit for dessert over such items as ice cream and cookies. When one school principal took the assignment literally and placed a spotlight over the fruit bowl, the choice of fruit nearly tripled.

In schools near Los Angeles, students who participate in garden projects show an increased preference for fresh vegetables over those purchased from the store. Equally significant is the fact that, as the desire for veggies goes up, the demand for sweets goes down. Creating appetites for healthy food is a great start.

Judith Mabel PhD, RD is president of Nutrition Boston in Brookline. For more information call 617-232-3073 or visit NutritionBoston.com.