SYDNEY, June 12 -- Single parents are far more likely to have overweight children, according to a new Australian study revealed Thursday.

The Australian Institute of Health and Welfare organisation is blaming the obesity trend on low incomes, inability to pay for participation in organized sports and the unaffordability of healthy food, News Corp Australia reported.

The study found there are more overweight and obese girls than boys, and almost one in four nine year olds are overweight and obese and by the time they are 14. It reported that 27 percent of teens are overweight or obese.

Girls are facing a harder struggle with their weight with the figures showing while 25 percent of boys aged under 15 are overweight or obese, 27 percent of girls are fat.

Having a sole parent, a low income family and living outside a major city are also risk factors for childhood obesity.

More than 35 percent of children with a single parent were overweight or obese, compared with 24 percent of kids those living in couple families.

The National Council of Single Mothers and their Children said one of the key factors driving obesity in these families is the children don't take part in organized sports because they can't afford it.

"Food is also a big issue," she said.

A study released earlier this year found a low income family would have to spend half its weekly wage to eat the healthy diet of lean meat, fruit, vegetables recommended in official national dietary guidelines.

Childhood obesity expert Sydney University Professor Louise Baur said obesity in children and adolescents is more common in people from disadvantaged backgrounds and lower income.

"So, part of the link with single parent households could be the link to lower income as well," she said.