I'm going to present the stats of childhood obesity over the past 25 years. I've used three data sources.
The first is the 2004 Canadian community health survey. In the past several years, when Statistics Canada produced overweight and obesity estimates, for the most part, they've been based on self-reported data. It meant that interviewers went out and asked people about their height and weight. We took them at face value when we produced our estimates. In 2004 we equipped interviewers with scales and tape measures, and they actually went out and measured the height and weight of Canadians.
When you base obesity on measured numbers, a different story emerges. Self-reported data for the most part result in lower estimates of weight, particularly for women, and higher estimates of height, particularly for men. When you put that together, you get higher estimates of obesity when you use measured data.
When you make comparisons across time and internationally, you have to make sure you have the same methodology. I made comparisons to the 1978-79 Canada health survey, which was also based on measured data. The national health and nutrition examination survey in the United States is again based on measured data.
The estimates I'm producing are all based on the body mass index. Obviously, people who are taller weigh more, so this is basically a weight measurement adjusted for height. It's calculated by dividing the weight in kilograms by the height in metres squared.
The obesity and overweight cut-off points for adults are well established. We have Canadian guidelines that are in line with the World Health Organization. Adults who have a BMI of 25 or higher are classified as overweight and 30 or higher as obese, and that's associated with increased health risks.
Things are less clear for children, but the International Obesity Taskforce recently recommended the cut-off points for classifying children as being overweight and obese. They basically took the cut-offs for adults and extrapolated them backwards based on the growth curves of kids. We now have cut-offs for age, sex, and specific years of age for children. I'm going to be producing estimates for kids aged 2 to 17 years.
In 2004 we found that 8% of Canadian children were obese. A further 18% were overweight, for a combined overweight and obesity estimate of 26%. It was up substantially from 1978-79, when only 3% were obese and 15% were either overweight or obese. A similar pattern emerged for both boys and girls, but it's still been quite a substantial increase over the past 25 years.
On chart 2, looking at it by age, as boys get older, going from 2 to 5, 6 to 11, and 12 to 17 years, the estimates increase. It's more stable for girls up to age 17, but then there's quite a large increase. Males and females again become more similar. It basically peaks at about ages 45 to 64. For adults, the obesity rates for men and women are about the same, at 23%.
Over the past 25 years, the increase among youth has been largest for the group aged 12 to 17 years. On chart 3, I have the distribution of BMIs and the percentage of kids with those various BMIs. Back in 1978-79, there were far more kids with lower BMIs, but then things changed. When you look after the cut-off point of 25, there are far more youth with those heavier weights, and these are the cut-off points for adults. It's very rare in a population to see a distribution shift of this magnitude. In fact, among 12- to 17-year-olds, the obesity rate has tripled from 3% to 9% between 1978-79 and 2000.
On chart 4, on the overweight and obesity rates by province, rates to tend to be higher in the Atlantic provinces, particularly in Newfoundland and New Brunswick. Lower estimates were observed in 2004 in Quebec and Alberta.
Chart 5 does a Canadian/American comparison. Generally speaking, estimates are quite similar between the two countries. American girls tend to have a higher obesity prevalence than Canadian girls do, but then if you compare just the white population to the white population, that difference disappears.
Chart 6 is back to Canada. It looks at obesity and overweight rates by ethnicity. The black population in Canada is basically no different from the white. The black bar looks a bit strange because the sample size was too low for me to produce an estimate. However, children of Southeast and East Asian descent are less likely to be obese, whereas aboriginal children living off reserve are significantly more likely to be obese. The obesity rate is 20% and the combined rate 41%, far higher than the overall Canadian rate of 26%.
In terms of some of the things that obesity is associated with, chart 7 looks at obese and overweight rates vis-à-vis fruit and vegetable consumption. The bar on the right-hand side indicates the youth who eat fruits and vegetables five or more times a day. They are far less likely to be overweight or obese than are those children and youth who consume fruits and vegetables less often.
Part of the 2004 community health survey is the nutrition component, in which we asked people to indicate everything they had eaten over the past 24 hours. Those data are just going to become available next month. In the future, we'll be able to look at obesity rates in relation to a whole host of nutritional factors, such as fat content of foods consumed, frequency of eating at fast food restaurants, and things like that. That will be researched down the road.
Chart 8 looks at obesity and overweight by what I call screen time. That refers to the number of hours that kids spend each day either watching TV, playing video games, or sitting in front of the computer. This slide shows measurements taken daily for 6- to 11-year-olds. You can see that kids who are in front of the screen for more than two hours a day are far more likely to be overweight and obese than kids who spend an hour a day or less in front of the screen.
Chart 9 shows the same thing for 12- to 17-year-olds. We measured screen time on a weekly basis for this group, but again you can see the same association.
We'd like to be able to make historical comparisons of screen time to see if it's going up. It's a bit difficult. Because of the computer, it's not quite the same. From the 1988 Campbell Survey of Fitness and Well-Being, we know that this age group averaged nine hours a week of watching television. In those days, basically, the video games were unknown and so was the computer. When we look at 2004, the TV viewing has just gone up by one hour, to 10 hours a week, but when you add the other components of screen time, it doubles to 20 hours a week. So there really has been quite a rise in screen time and the more sedentary activities.
Chart 10. For the most part, the negative health consequences associated with obesity manifest themselves only in adulthood, but as part of the survey we did ask children 12 to 17 to rate their health as being excellent, very good, good, fair, or poor. You can see there's already an association: normal-weight kids are far more likely to have positive perceptions of their health than are overweight or obese children.
I have just two last thoughts. Even for the 12- to 17-year-olds, the numbers we're seeing, even for the overweight category, are of concern. We don't have Canadian data on longitudinal studies yet, but a recent study that tracked adults over time showed that among overweight adults, the ones who were the most likely to become obese were those in their twenties. So there's concern that these overweight adolescents are going to end up as obese adults, with all the negative health consequences associated with that.
The other point is that once an individual is obese, sustained weight loss back to the normal weight range does not happen very frequently.
One last thing, too, is that increasingly we're seeing obesity happening at younger and younger ages. So in the next generation we're going to be facing people who have been overweight for many more years and with all the complications of the chronic conditions associated with obesity.
Thank you.