I’m not an athlete, and BMI is still bollocks

I’ve been on a campaign since January to get back to my pre-Canada weight (damn North America your portions are too big). I have a few metrics for checking my progress: the numbers on the scales, which of my old clothes fit again, and Body Mass Index, BMI.
Being an overweight woman, I read a lot these days about fat shaming and the like, and BMI often crops up as an unfair measuring tool.

Let’s be clear: it is a crappy tool. But you know what’s really unhelpful in a lot of these blogs and articles? Focusing on the fact that muscle weighs more than fat, and therefore ‘BMI will even class elite athletes as obese!’ That’s very true, but how the hell does that help me? I’m not an elite athlete. I’m not an athlete of any kind. My primary form of exercise is walking, which I do on average for 40 minutes four or five times a week. It’s building up a little muscle yes, but I am not delusional enough to think that the problem with my weight is anything to do with having more muscle than fat.

So telling me this again and again does nothing to convince me of the ills of BMI. It was only a couple of weeks ago that I managed to transition from the ‘obese’ to the ‘overweight’ BMI category, and this felt like an achievement.

But ‘obese’ is supposed to be the category where your health is seriously at risk, and I have not been a burden on the healthcare system for the past few years. There’s a part of me that knows BMI is still bollocks. So, for you and me, I’ve rounded up some reasons, other than fat vs. muscle, why BMI is a bad indicator of weight-related health status.

1. The relationship with height is flawed
The formula for calculating BMI uses the square of a person’s height, but short and tall people tend to have different builds. Tall people are not scaled up short people. There are a range of estimates for what exponent could work, but for now 2 remains in use

2. It takes no account of frame size
You can actually have big bones. Bone is dense and weighty. Not only does BMI not account for the difference between fat and muscle percentages (and everything else), it also doesn’t account for bone make-up. Body composition is important.

3. It takes no account of body proportions
Waist, hip, neck, wrist, chest, you name it, they’ve measured it in an attempt to better match body size to health outcomes than BMI. Where you hold fat on your body affects which organs are impacted. The best at present seems to be the waist to height ratio.

4. It’s not a good indicator of actual health
Obesity increases the risk of developing heart diseases, type 2 diabetes, cancer, and sleep apnea, among others. However, recent studies have shown that obesity as predicted by BMI may also protect against death from all causes, as well as death due to stroke, heart failure and diabetes. Confusing? Yes. But it is proof that BMI is not a good indicator of true obesity, and therefore not a good indicator of health.

*

I decided to check my waist-to-height ratio after writing this. One site helpfully put the results into categories, which it seems to have pulled out its ass, one containing the descriptor ‘Healthy, Normal, Attractive Weight’. Who are you to say what’s an ‘attractive’ weight assholes? It makes me want to create one of those site that’s like www. whatsmybodytype .com and just says things like Slammin’ and Day-um!.

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