AIBU to tell you that BMI doesn't apply to everyone!

[Randomuser456]

Foreword I know it's a blunt tool, etc, etc ,etc... and I DO exercise more than the average person (don't really ift heavy) but I've always thought my clothes size doesn't match my weight.

Anywho according to the Navy Body Fat formula I'm around 27-28%

A BMI extrapolation would put me at 38%. By reversing that calculation someone with my BF% is around 15kg lighter than my current weight.

Anyway just a public service announcement :)

According to the NHS I could gain another 1.5 stones and still be (just) in the healthy BMI category.

Yet I would be definitely be uncomfortably fat.

It's very confusing.

Yes. The people to whom it doesn't apply will know. For the rest of us - reasonable basic measure of health (which could be contradicted by more sophisticated one - but a good starting point)

No it doesn't. I can imagine someone tall and muscular could look too high. I have brittle bones which I think make me weigh less. I look similar to people with a low but healthy BMI, but mine comes up looking exceptionally low.
As long as you feel healthy, can move freely with energy and aren't in pain and can live your life in a satisfying way that's the main thing.

Yeah yeah yeah. It's a common refrain from people who don't like their BMI results 🤷‍♀️🥱

Of course it doesn’t apply to everyone. I can’t imagine it applies to those that have lost limbs for instance! But for everyone else it provides a reasonable estimate, speaking as someone sporty, very muscular, could do ith losing half a stone. BMI = 22.8

What’s your clothes size?

It's not for everyone. My DH used to play rugby, he has very big muscles on his legs and upper arms. He doesn't carry much fat but his BMI is always in the obese category presumably because his big muscles are heavy.
I'm always in the ideal weight category but I definitely have more fat than him!

The weight range in the 'healthy' category of BMI is pretty broad...

I'm a size 8

28% body fat is still pretty high though. Surprised you're a size 8 unless you're short maybe.

If never heard of the navy body fat formula before so did it out of curiosity. My body fat is 21% apparently, I wonder how accurate it is? It seems a bit weird that you would take the navy body fat formula as gospel but declare that bmi means nothing.

Do you mean your bmi is 38? In the severely obese category?

Same, and using the BMI extrapolation it's more like 30%. Using my scales my BF% is more accurately 26% so somewhere in the middle. It's all population estimates, so that makes sense.

I could stand to lose some weight/tone up and have a lower BMI and BF% than OP (also size 8) so not sure what the point of this thread is, other than to make excuses.

Well I said 28% is still high but according to that formula I have 30% which I imagine is because I don't have much of a waist but that's my bodyshape so not sure how accurate that is. My BMI is 23 and I could lose at least half a stone.

BMI is a made-up number that provides some indications at a population level about general health.

It is not a predictor of health for any individual, if that's what you mean by "doesn't work". Which is how it's touted about.

28% is not high, it's considered normal/healthy. Anything below 25% is considered athletic/fit.

This. I'm 5"8" and according to bmi could be between 8.10 and 11.10 and be considered healthy. When I weighed 13.7 a couple of months ago and saw I was well into the overweight category I was pissed off 😂 but friends/family insisted I didn't need to lose weight, I was in a size 14-16. But vanity sizing is ridiculous nowadays and loads of stuff has stretch in.

It gets trotted out a lot on here but we've lost sight of what a healthy person looks like. I've lost two stone now and feel amazing - I felt shit before! I'm now in a 10-12 but still have another stone to go to be nearer the middle of the healthy category. I'm already getting the "don't lose anymore weight" comments.

I guess for people who are a large frame and lift heavy weights it may not be accurate but that is very rare.

Apologies I much more often hear body fat spoken about for men which is quite different.

I don't really buy in to the navy formula though as most women's fat is below waist level and there is no accounting for how muscular a build someone has.

Are you saying your bmi is 38 OP?

That's not the only one I used...I used a couple of other equations and they all gave similar %s

The difference is that they as for the different measurements as opposed to just weight Vs height.

The average person with my BMI (of 28) has (in theory 38% body fat)

It's not that the BMI doesn't apply to everyone, but the formula for deriving body fat from BMI is incredibly blunt. And so is the Navy BF formula to be fair. They also make different assumptions (age is relevant to BMI body fat, but not to Navy BF). They are estimates, you can't reverse engineer 2 estimates and expect to come up with the same answer. If you really want to know your body fat, get it measured properly.

I think it will always put me as more overweight than I am as I have abnormally short limbs (out of proportion). At the moment I am overweight anyway though just frustrating when I wasn't really and it said I was!

No, BMI doesn't apply to everyone and it doesn't apply to you.
However if I had a pound for all the times I have heard someone say this for whom it really should apply then I would be mildly richer than I am, which would be nice.

It's not a public service to announce that there are flaws in it. Most people should take notice of it and if they're not sure they should seek advice from someone qualified to do so.

Using BMI my body fat is 28%. (Lower side of healthy weight range according to BMI.)
Using the navy calculator it's 19%! And the added info puts me as "athlete" 🤣
I exercise most days but athlete is pushing it, and hilarious for anyone who has seen me attempt sport.

If I was about 15 years younger I'd be spot on according to the calculator. It doesn't seem to take into account menopause specifically, more a gradual thing. Why would my "ideal" body fat% differ between 25 and 35, for example? No medical reason, surely?

I'm classed as obese, and have had weight loss clinic offers from the GP 😂. I'm size 14, so definitely overweight, but obese??! Quite the shock, I can tell you. I swim 3km per week and I'm 5'6 so not tall but definitely not short.

It's a tool more useful at a population level based on averages. You can see trend changes.
The 'blunt tool' argument only goes so far.
The reality is that most people with a high BMI won't be muscle-bound rugby players with a small body fat %
BMI is but one tool used to assess someone's health.