While obesity rates for adults are up, obesity rates for Canadian children aged five to 17 decreased slightly between 2004 and 2015, according to data recently released by Statistics Canada.

The data uses BMI or body mass index to identify obesity. Body mass index is measured by dividing weight by height. A BMI of 18.5 to 25 is considered "normal" and anything over 30 is considered obese.

In the latest statistics, boys who were considered obese (children who were had a BMI over 30) fell from 15.7 per cent to 14.5 per cent between 2004 and 2015. For girls, the numbers went from 10.8 per cent to 9.5 per cent.

British Columbian children followed the national trend. Boys considered obese dropped from 16.8 per cent to 11.1 per cent. For girls, the number dropped from 11 per cent to 9.1 per cent.

Is BMI the best tool?

University of British Columbia obesity researcher Angela Devlin says while it's good news obesity isn't increasing among children in Canada, she noted since obesity rates among adults increased, it could mean children who were overweight were simply moving towards obesity as they grew older.

In addition, Devlin says BMI is not the best tool to measure health.

"In adults this has been debated and it is now well accepted that other markers of adiposity [ie. obesity] like waist circumference are better indicators of health risks such as type 2 diabetes," Devlin said.

She adds BMI doesn't work for all children.

"For example, a teenaged boy who is a football or hockey player can easily have a BMI that puts them in the overweight-obese category but that is because [they have more] muscle mass, not fat," she said.

But Dr. Shazhan Amed,  a pediatric endocrinologist at B.C. Children's Hospital — who called the data results extremely promising — says for large population studies like this one, BMI is the best possible tool.

"Are there better measures? Probably," she said. "But to do those measures on a population level is unrealistic and unfeasible ... It's a good enough indicator to give us data that tells us our progress."

The data collected is based on the height and weight of respondents measured in the 2004 and 2015 Canadian Community Health Survey.