Childhood obesity is on the rise among Canadian children and experts say it is time to take action to ensure a healthy future for the country.

More than one-third of Canadian children aged two to 11 were overweight in 1998-99, according to a Statistics Canada report released Friday. About half of those children were considered obese.

"We know that 70 per cent of obese youth persist their obesity into their adulthood," Claire LeBlanc, an Ottawa pediatrician told globeandmail.com on Friday. "If we don't do something about this in childhood, chances are they will continue to be obese as adults and that increases health risks."

According to the report, in 1994-95, 34 per cent of children aged two to 11 were overweight, with an estimated 16 per cent classified as obese. By 1998-99, 37 per cent of children in that age group were overweight, including 18 per cent who were classified as obese. These observations were made on the basis of the international definitions for child overweight and obesity.

"This certainly reinforces the fact that our youth are getting heavier, and it is a concern," Dr. LeBlanc said. "We have to realize as parents of children in Canada that these particular children are also suffering ill effects because of it."

The study by Human Resources Development Canada and Statistics Canada started in late 1994 and early 1995 and went through three cycles to 1998-99.

Dr. LeBlanc says the numbers can be attributed to a number of factors.

"Some of this is stemming from inappropriate diet," she said. "But it is also related to inactivity. These kids are going to run into problems with hypertension and Type 2 diabetes."

More boys than girls were overweight. In 1998/99, an estimated 35 per cent of girls and 38 per cent of boys were overweight, including 17 per cent of girls and 19 per cent of boys who were classified obese.

Age differences in levels of obesity were also seen, as fewer of the older children were obese. One in four children between the ages of two and five were obese in all three cycles, compared with one in 10 children aged eight to 11.

"In recent years, childhood obesity and low levels of activity have emerged as important issues facing Canadian children," the report said.

The study also found that higher proportions of children living in low-income families were overweight and obese.

In 1998/99, one-quarter of children aged two to 11 living in families with incomes below the low-income cut-off (LICO) were obese; only 16 per cent of children in families above the mark were in this weight category. The proportion of overweight and obese children decreased as family income increased.

A poll released in April by the Canadian Pediatrics Society (CPS) found that 63 per cent of parents know their children are not fit but blame homework, television and the Internet for the weight problem.

Dr. LeBlanc, chairman of the CPS Advisory Committee on Healthy Active Living for Children and Youth, says the medical, health, recreation and education industries must combine to tackle the problem.

"If we work together in all facets we should be able to come up with reasonable solutions that will be long-lasting to these children," she said.

"These issues can't just be dealt with at the family doctor's office. Policies need to be made at the regional, provincial and national level to make changes that will make our children more active."

In April, Health Minister Anne McLellan unveiled Canada's Physical Activity Guide to Healthy Active Living. Later this fall, supplementary documents to the guide will be released.

"The documents are resources for teachers and families," Dr. LeBlanc said. "The six documents will help us to better utilize the Physical Activity Guide more appropriately."

Statistics Canada measures obesity using the body mass index (BMI), which is based on both an individual's weight and height. Calculate BMI

International cutoffs for children were used to classify children as overweight or obese. The child cut-offs are age- and gender-specific for children aged 2 to 20. For example, a boy aged 12 who was 1.1 metres tall, would be considered obese if he weighed 32.5 kilograms or more.