Thanks again for the invitation as extended by Mark and Cora.
I've been in obesity research for ten years, and I actually went to graduate school when I saw this problem starting, with the intention of trying to solve the problem. It is nice to see that we're finally starting to get the attention this problem warrants.
I am an epidemiologist. What that means is that I look at the surveillance of obesity. I look at the risk factors for what's going to predict who develops or has obesity, and I look at what the outcomes are of obesity if you have it. I work a lot with children as well as with adults.
Today I'm primarily going to be sharing results with you based on a very large international survey I'm involved with. This survey is called “Health Behaviours in School Age Children Survey”. It's an international survey conducted in 35 countries every four years. The team of investigators that I work with at Queens are responsible for conducting this survey in Canada. We collect data every four years on about 10,000 kids from grade six to grade 10 all across Canada. The nice thing about this survey is that we can compare ourselves with other countries to see how we're doing. The other countries in this survey are primarily European countries, as well as the United States, so we're comparing ourselves to industrialized countries.
I'm going to draw your attention to the first figure. This figure shows the prevalence of inactive youth in the different countries. So in this case you want to have a low bar. It means you have fewer youths who are physically inactive. And as you can see there, Canada falls about fourth to the right. So compared to these other countries we're actually doing quite well, which is surprising. I see a lot of puzzled faces out there. I was also surprised when this result came up.
But I think we also need to look at the axis that shows that the prevalence is above 50% inactive within Canada. So even though we may say we're doing well compared to the Europeans, we're not doing well within our own country. More than half of our youth are inactive, and this is using European guidelines for physical inactivity, which are very conservative. As Cora mentioned before, if we use more stringent guidelines, as we tend to do in Canada, fewer than one in five of our adolescents meets our own physical activity guidelines.
If you now turn your attention to the second figure, it shows something similar but looks at the prevalence of being overweight instead of being physically inactive. So again you want to have a low bar. In Canada, unfortunately, we do very, very poorly. This shows the results for overweight. You would see the same patterns for obesity. We're right up there with the champions in Europe, which are the Mediterranean countries, and the United States. We're right up there. We're the fattest among the fattest of the fat. No questions about it.
So now you say, how can we be among the most active and at the same time among the most obese? It's a very puzzling observation, and I always get asked that question when I present this. And as Mark implied, we think there are some issues there with the data quality, since our frame of reference has really changed in Canada with regard to what counts as physical activity compared to what counts as physical activity in European countries.
The much more important thing is that when we look within our Canadian children, as shown in figure 3, we see clear gradient relationships between the amount of physical activity that youth have and their likelihood of being obese. So the bar on the far left represents the most inactive children, and the bar on the far right represents the most active youth. And we can see that as children get more active, the likelihood of obesity goes down. I can tell you as an epidemiologist, when I see risk gradients that are this strong, I'm doing cartwheels in my hallway. These are very, very strong risk estimates. When we look at the nutrition variables, they don't come out as being strong predictors of obesity in this particular group of individuals. So what that's suggesting to us is that we really need to be focusing on the physical activity side of the obesity problem a little bit more than the nutrition side.
I'm going to skip my next slide--because Cora has already spoken about many of these factors--and move into the question of how sedentary we are. We have some really good data in the HBSC, based on our asking the children how many hours they spend in front of the TV and in front of the computer in their free time. This does not include homework time. The Canadian Pediatric Society is recommending that our youth spend less than two hours in front of the screen. Less than one in five children in Canada meet those guidelines.
The average adolescent in Canada spends almost 35 hours a week in front of the computer or TV in their free time. That's almost a full-time job. If you calculate that out for the year, they spend more time in front of the screen than they do in the classroom over the course of the year.
Clearly, there is time to be active. There's lots of time. That is further supported by the observation that if you actually look at the relationship between how much time children spend in front of the screen and how much activity they do, they're not related very strongly at all. So there's lots of time, even for the active children, to sit in front of the screen.
That leads me into another point where, when we are talking about decreasing screen time, it's easy to tell your kids to turn the TV off, to get away from the TV, to get away from the computer. But what will happen if parents do that is most likely the child's going to move to another sedentary behaviour. The randomized control trial data clearly show that you actually need to not only reduce the TV watching, you need to be emphasizing that it be replaced with active behaviours.
I am now going to switch over to figure 4. The reason I want to show this figure is to bring to light the issue that not all sedentary behaviours are the same. In terms of obesity, television viewing seems to be the biggest predictor of obesity in the sedentary behaviours. This is showing that, as you go from those who watch the least amount of television to those who watch the greatest amount of television, the likelihood of being obese goes up twofold.
The additional point I want to raise here is that these effects are independent of how much physical activity the children are doing. In other words, if you took two children or youth and matched them in terms of how much physical activity they're doing and they're doing the same amount, the child who is watching the most television is more likely to be obese than the child who is watching lesser amounts of television. So there seems to be independent effects of physical activity and television viewing on obesity.
The last research point that I want to bring to your attention is shown in figure 5. The reason I want to bring this to your attention is that when we are talking about obesity, quite often we get really focused in on weight, and that's our outcome. We're worried about the weight, not actually worried as much about the behaviours as we are about the outcome. For obesity that's a very bad thing.
The reason I say that is because when we look within obese individuals, there are clear differences in health, depending on how physically active they are. You can be fit and fat. It is possible. So if you look at figure 5, that is an example of obese girls. Again, these are all obese individuals, graded according to physical activity participation, and as you go from low to high, the number of psychological health problems that these girls had went down in a clear pattern.
Again, we need to get the message across that it's not only body weight; it is the behaviours themselves that contribute to body-weight issues. They have impacts independent of any effects on body weight.
I am going to finish off. Really, this is a plea for help. We've really learned a lot in recent years in the obesity community. When I go to the United States and I talk to my American colleagues, they are amazed at what we have done in Canada, given the size of our country and the size of our research community. But there are more unanswered questions than there are answered questions at the moment, and the quality of data that we have in our surveys in Canada compared to that of the Americans is embarrassing. Plain and simple, it's embarrassing.
There are many more questions. I've only given three examples on that sheet, but there are many more questions and we do need more research money and support.
Thanks for your attention.