Why BMI is not fit for purpose

There has always been the arguments and constant articles criticising BMI and it’s used in modern health. Is it an idea that is simply out of date? Was it ever right to begin with? Today I want to take a pretty personal slant as to why I think BMI is not fit at all for purpose. Shall we?

Scientifically it doesn’t make that much sense

To the point that the mathematician who invented it stated that it shouldn’t really be used to measure the fatness of a person. Yes you read that right, it is meant to work out the mass, not whether someone is overweight. When I say it’s inventor I think it is worthwhile detailing how old BMI is, it is 190 years old. Now surely someone has seen that a scale 190 years old (and was fudged to make the theory right) needs a fresh look no?

It also doesn’t calculate maybe the most important part of figuring out if someone is overweight… Their waist size. It is a general convention to assume that if a man has a waist of over 37 inches (woman 31 inches) then they are overweight. Fair enough, that makes a lot of sense, though I am sure there are exceptions to that rule.

BMI also ignores what is in that mass and I am not just speaking about muscle mass, but about the muscle tone and the bone mass and the water mass.

Why does the NHS keep pushing it?

As the BBC after they were criticised for using it to measure obesity levels with people who took part in their survey. It is nice and easy. You weigh yourself and see how that connects to your height. Nice and easy maths dictates you a number, that’s it. Height and weight.

They also say it is the best method doctors have to measure obesity levels. But surely doctors have access to methods of working out someone’s body fat index? They followed up this up by stating that when it is wrong to say for rugby players and athletes that it is only wrong for 1% of the population. Now I don’t know if they are going to the gym a lot but certain trends have been booming for quite a while now. More and more people of both genders are not just being cardio bunnies at the gym.

I know that BMI has never classed me as healthy because for me to be in that healthy range would require me to be in the 11 stone region and I can say that unless I shredded fat when I was at my lightest, there was no chance on earth that I was going to get to that number. For my build 11 stone was just an unattainable number and yes, maybe I could be classed as an outlier and that BMI is just a general way of understanding someone’s mass, but it had mine wrong and sometimes that can lead to worse things.

UCLA carried out research and found that people in that 30% of people within the healthy spectrum were in fact not healthy based on other health data that they provided. BMI is not a one size fits all system and the NHS, BBC et al need to stop pretending that it is. They may accept it is not perfect, but to say that other ways to measure the body fat of a person are too expensive is nonsense, but I will get into that later…

The mental aspect of it

When I was at my worst and even last year when I regained the weight I was in the morbidly obese range, but when I got down to my lightest and was working out via running, the gym and weights I was into the 13 stone region. I had loose skin, but I was generally quite fit and a lot fitter than a lot of people in the healthy range. Why do I bring that up? Well, for my height the 13 stone region was still seen as overweight. I was in size medium shirts and was getting closer to a 32 waist. I was still seen as overweight and overweight by how much? 1 stone and 8 lbs. In their mind, I had to lose another 23 lbs to be classified as healthy…

For someone who has had trouble coping with their weight and their weight loss to read that was devastating, utterly devastating. That no matter how great everyone said I looked or how great I felt. I was still overweight and let me clarify something to fully cement how detrimental this was to me. I was in the idea of BMI closer to being OBESE than I was healthy. At my 13 and a half stone, I was considered borderline obese. I am not a tall guy but I am broad and I was working out a lot. I was not one of those elite athletes and I certainly wasn’t in the 1% of the population for muscle mass. I was doing normal workouts and not too heavy weights and I was in what I classed as normal clothes. But I am almost obese according to BMI.

I will not lie when I say that this broke me a little. I didn’t know what to do and it really hurt. I thought I was doing everything right, according to every other system I checked I was healthy, yet this system said I wasn’t and if you are struggling mentally, guess what? You are going to believe the one that is negative. I did and it took a hell of a lot of research to help correct my brain into thinking that no, it isn’t me that has the problem. It was BMI.

If it is wrong, what is right?

Ideas floating around for simple measurements is to go by height vs waist ratio. This makes sense due to the importance of the waist measurement and how the NHS link it to diabetes. It also seems a lot fairer to those who are healthy but just have a lot of mass. Of course, some body shapes would be hit by this, but a far sight more wouldn’t.

Obviously, there are some scales that are getting pretty close to reading spot on, but is that enough for a doctor to switch from the easy formula of BMI? Would a doctor go with these newer methods in place of what they know? I doubt it as I do not believe affordability is the issue, I believe it is an easy issue. Surely a top of the range scale could get a close look (I accept not exact) and provide good enough readings instead of “Your BMI states this number, so you are obese”. There need to be more details. Maybe I complain a bit more because I love statistics, so knowing all of the information is cool to me, so then I can improve on them all instead of just getting to 25 on the BMI scale. What is my fat %? Should a doctor not WANT to figure that out to help their patient?

In the end, we know unless a lot of doctors make a fuss about BMI it isn’t going to change, but try not to get it stuck in your head if you are trying to lose weight or be healthy and that number states overweight, obese or whatever. If you know things are going well and you see progress or retainment then it’s all good. I felt great and then BMI snuck on me with all the bad thoughts and derailed me for a little while. You can get past that if it happens to you.

That’s all for today, thanks for reading. What do you think about BMI? Let me know.



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