TUESDAY, Jan. 25 (HealthDay News) -- It's hard to help overweight children lose weight, and keeping it off over the long-term is even tougher. But obese children whose parents took classes on the importance of healthy eating and exercise lost weight and kept it off for the next two years, according to a new Australian study.

Researchers said the study shows that targeting parents -- rather than the children -- can help stave off weight gain in children aged 5 to 9.

"We believe it makes developmental sense to involve only parents," said lead study author Anthea Magarey, a senior research associate of nutrition and dietetics, at Flinders University School of Medicine in Adelaide, Australia, where the study took place. "It takes the stigma away from the child and supports a whole family approach."

The study findings were released online in advance of publication in the February issue of Pediatrics.

For young children, parents play a huge role in their eating and exercise habits, Magarey explained. The kids are still spending most of their time at home and eating most meals at home. Parents buy and prepare food, and decide what and how much kids can eat. They are responsible for providing opportunities for children to be active and can set rules for TV and video game use.

The researchers enrolled mostly mothers of 169 moderately obese or overweight children aged 5 to 9 years in a six-month "healthy lifestyle" course, in which parents were taught about portion size and reading nutrition labels, being a good role model for their children and setting limits. (Half of the parents also took a parenting course, although the study authors found little difference between the two groups).

At the end of six months, children's body mass index (a measurement that takes into account weight and height) dropped an average of 10 percent, as did their waist circumference. Eighteen months later, the children had kept the weight off, the investigators found.

In the United States, about 17 percent of children and adolescents aged 2 to 19 years are obese, a number that has been increasing since the 1970s, according to the U.S. Centers for Disease Control and Prevention.

About 24 percent of U.S. children aged 2 to 5 are overweight, meaning they have a BMI in the 85th percentile or above for their height and age. That number rises to 33 percent among children aged 6 to 11, according to the CDC.

After the healthy lifestyle sessions, parents said they felt more comfortable saying "no" to their children's demands, setting limits on the type of food the children could eat, limiting the amount of time they spent watching TV or playing video games, and establishing consequences for breaking the rules.

Parents assessed their own current eating patterns and set their own goals for change, such as limiting TV to no more than two hours a day, doing more active family activities and making small dietary changes that can go a long way, such as eating more fruit and vegetables, using reduced-fat dairy products and drinking fewer sweetened beverages such as sodas.

Kathy Kolasa, a professor of nutrition services and patient education at East Carolina University in Greenville, N.C., said she does not believe children have to be excluded from obesity prevention programs because of the risk of stigmatizing them.

But making sure parents know about nutrition, portion size and how to make sure their children are getting enough physical activity is critical.

"In my experience, there are plenty of parents who tell me they know what to feed their kids and that they are eating healthy," Kolasa said. "When we analyze their diet, they are surprised that they are not following or providing age-appropriate portions and healthy foods for their kids."

As for the parents included in the study, their weight did not change over the two years.

More information

The Children's Nutrition Research Center has more on healthy eating for kids.