Body Mass? Irrelevant.
A study of 900 Vancover-area teens found that the BMI is meaningless as an indicator of physical activity and healthy eating.
According to [Dr. Catherine] Sabiston, who is also director of McGill’s Health Behaviour and Emotion Lab, the results showed only a very weak correlation between physical activity and healthy eating, and virtually no correlation between an individual’s BMI and his or her level of physical activity. The study was undertaken to test a comprehensive model of physical activity and healthy eating behaviour in teens aged 15 to 18, partially in response to two perceived problems with existing research in the field.
It's noted that the group studied is traditionally underrepresented in studies. (Got that?) There were some interesting differences between the genders:
The study also found a significant difference in the way boys and girls approach physical activity and healthy diet. Boys, Sabiston said, need to attach value to a healthy diet and feel confident in their ability to follow a healthy diet before they’ll actually do it. Girls, she said, regardless of how they feel about their ability to eat a healthy diet, only need to feel it is important to do so before they’ll eat properly.
I wouldn't be surprised if this was due to the idea that women are "always" on diets and how that's been deemed normal. I found the value requirement for boys to be interesting, because it demonstrates that boys are held to a totally different standard... and in turn, have to have something in mind when undertaking a diet.
Regarding these results:
“A lot of people are surprised,” Dr. Sabiston said, “but when you think about it, BMI doesn’t have a huge impact on physical activity. And in terms of diet, it actually makes sense that someone who is not happy with their body might try to eat more healthily.”
The problem, though, is that many people choose not to think about it. Classification is something we as humans like to do. We've been led to believe for years that the BMI is the Golden Standard when it comes to health, in particular because important things like healthcare eligibility are tied into it... which classifies people into "healthy" and "unhealthy" buckets. "Good" and "bad". Et cetera. And since the idea that the BMI is important is perpetuated by a lot of people, including prominent folks with vested interests, it becomes so. Although the truth is entirely the opposite: the BMI is irrelevant.
There's a great quote at the end of this piece, too. Emphasis mine.
What this study really says, Sabiston explained, is that one cannot assume that someone who is physically active necessarily eats a healthy diet – or the reverse, that someone who is more sedentary or has a high BMI by definition eats a diet of junk food.
“This study drives home the point that as a society, we’re primarily focused on extrinsic things like appearance and weight versus the betterment of health,” Sabiston said. “From a public health perspective, this means we should probably focus on people who are at a healthy weight or even underweight, and emphasize that healthy eating is not just about weight-change.”
Unfortunately, in tandem with the whole "not thinking" thing, it's a hell of a lot easier to use fat people as scapegoats. So here we are in this fabricated crisis. In the interim, we must continue to point out that BMI is meaningless; studies like this make our task just a little easier. [Thanks to LLW!]