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 :)

I tried to get down to my healthy BMI range. I was still about a stone and a half off the top end and I looked like shit. You could see every bone in my face.

Sacked it off and lived quite contentedly for the following 20 years.

My BMI is 24.5. Navy calc puts me at 28%. My waist to height ratio is bang in the middle of healthy range. Much for muchness as blunt tools in my opinion. I'm a reasonably active fluffy size 12. I think I look on the fluffier end of ideal, and all calculators put me more or less there.
There's a lot of wishful thinking about this stuff. Everyone seems to beleive they are the exception.

I had also never heard of the US Navy method and I now feel much healthier, so thanks OP! I am right on the cusp of average and fitness and on the Jackson & Pollock body fat thing that was included on the online calculator I used I only need to lose 1.2kg of fat to be “ideal”. This has cheered me right up as even when I am v trim and putting in lots of effort diet and exercise wise I can never get my bmi under 23.

The BMI doesn’t apply to anyone.
It is only suitable for use across a population, not for an individual.

It’s only (mis)used because it’s an “easy” way to judge someone’s weight/size/health, despite being inaccurate and inappropriate.
There are some great articles and podcasts about why it shouldn’t be used.

Couldn't pinch an inch anywhere

I had completely forgotten about the 'pinch more than an inch campaign.

Edit: Why does MN hate Youtube links...

Every time I click on a topic re BMI I’m reminded that Mumsnet is the land of athletes and outliers

I’ve been calculating BMIs for professional reasons for about 15 years.

Not once, not ever, not even one single time, have I seen someone with a BMI in the obese range who was not clearly, noticeably obese.

It doesn’t matter, they may still be perfectly healthy, but they are obese.

I’m only 5ft and have heard BMI doesn’t really work with very short or very tall people. I’m a size 12-14 but obese according to BMI (I know I’m a little overweight) and could lose 1/3 of my body weight to have a healthy BMI. I’m sure I’d look unhealthily thin if I lost that much weight

Yea. In reality whenever I hear the 'BMI is outdated/inaccurate/bullshit' trope - it is always said by an overweight or obese person, followed by 'my husband/brother/friend/relative is a brick shithouse rugby player/7 foot muscleman Olympian and according to BMI he's morbidly obese (head tilted chuckle)'. How is it relevant when said by a short, overweight, sedentary office worker, I have no idea.

For non 7 footed non Olympians - the vast majority of the population - BMI is accurate enough. Obviously not perfect, but works fine as a guideline.

I know that I am generally a healthy weight, but my height at 5”1 pushes my BMI right up to just under the overweight category. I have wider hips and a curvier figure instead of a straight up and down figure and that’s how I carry fat across my body. Muscle is indeed heavier than fat so if you do a lot of lifting weights for example you might have a higher BMI on paper, but in reality you might be very healthy and fit.

The only thing I would say is that the term ‘BMI’ itself seems to be used as a verb frequently nowadays, and comes across as a bit dissociative when people prefer to describe themselves as ‘high BMI’ rather than overweight or even plus sized, as if the ‘high BMI’ status absolves the actual reality of being overweight.

I lift very heavy, eg think 100kg deadlift, 60kg bench and 80kg squat. I weight 65kg.

My BMI is 25, and my bodyfat is around 25%. I look very toned (eg visible triceps biceps delts etc. I’m a size 10.

Yes it’s a blunt tool, as clearly if I gained 2-3kg I would still be healthy. However if I go much over 65kg my size 10 clothes start to feel tight.

Who are you, Rebecca Adlington? I swim 1km, 3 times per week and when I'm asked by medical professionals about the exercise I do (as part of routine check ups) they say "that's a good amount". The only thing they've recommend for my age (46) is more weight bearing exercise due to perimenopause and inflammatory arthritis taking its toll on joints. Even when I was at my fittest and healthiest (normal bmi) I was a size 12. Mind you, I've got enormous knockers. Not a boast, I wish i didn't!

I'd love to spend hours in the pool, and a couple of hours doing 120 lengths, 3 or 4 times a week would be a luxury, believe me!

BMI has a range of around 2.5-3stone in the healthy weight category so it allows for frame size and pear shapes and whatever because it’s a ratio of height to weight. It works if you are tall or short or work out a few times a week. It’s a rough guide. Mine is 21 and I could lose a stone to ge honest to look better. How anyone in the overweight or obese category can say they aren’t in race overweight is beyond me. Rivers in Egypt spring to mind. I lost weight when I stopped bullshitting myself about what I was eating and ate better and did more exercise. My body fat is around 24%. I have muscly arms and legs but plenty of lard too.

What about overweight though? Have you never seen someone where you thought they do not look overweight but their BMI says they are?

I have never heard of the US army thing before and I think I am being a bit slow here as I don’t get the figures, would someone mind explaining please?

The US army method calculator has given my body fat with their method and the NHS method which don’t bear any resemblance to my BMI (way above) are they supposed to ?

For body fat to lose to reach ideal it says 16.5kg. Does it literally mean total amount to lose or is there some other calculation I am supposed to do? 16.5kg loss would put me a stone over top end of my BMI and I know from experience that I will need to be top end of BMI or below for my blood pressure to normalise. Many thanks.

@Seaitoverthere I am not sure either, but that figure given for loss is of fat loss not weight loss and obviously it is tricky to lose fat without losing muscle, might it be that?

Also someone I follow on Instagram, Kelsey Wells who is a fitness influencer is overweight by BMI standards. There will probably be someone along soon saying how fat she is but I can’t really see a doctor sitting down telling her that she’s at risk of various diseases due to her excessive bodyweight. At the same time, I know some people of normal BMI who have rolls of fat on their stomach.

Nothing weighs more than something else. 1lb is 1lb.

Muscle is smaller in size and more dense. Fat is fluffy and takes up space. All this means is muscle takes up less space. It weighs the same. It’s also very easy to gain fat and much harder for women to gain muscle. It’s easy to lose muscle and hard to lose fat. You can’t replace fat with muscle they are different tissues. Your muscle sits under your fat. The only reason you can see abs on someone is when they have quite a low body fat. We all have ab muscles, we all have the same muscles in the same places just you might train muscles to grow, which is actually quite hard to do, takes ages and females have a limit of muscle growth compared to men, and it’s why people need steroids and hormones to get that big pumped up look. I can honestly say in 2 years of working out I probably only gained a few kg of muscle mass, just you can see them more easily as I dropped 60kg of fat mass. I could not have gained that in muscle without steroids

Well 1 square cm of muscle weighs more than 1 square cm of fat which I’m sure was what pp meant 🙄

But this is really misleading that muscle is heavier than fat when it’s not true. Fat just takes up more space because they are different densities. Genuinely is important to differentiate between the 2 because people do not understand the difference and how hard it is to grow a muscle to make it larger and they are not interchangeable at ALL. You can’t replace fat with muscle. Nothing can be converted from one to the other. Yet isn’t that what half the internet is shilling? Ladies - get a beach body and convert your fat to muscle (impossible), or well I lost fat weight so I can see muscles now (doesn’t mean the muscles got bigger). Easy to lose muscle when you go on a weight loss as well

That makes sense, I did wonder if it was something like that. Thanks. Personally I feel BMI works well for me but can see there are some outliers.

I still think it must depend on build, for all heights. I'm less than 5ft tall and almost in the middle of the acceptable range. I could (according to the chart) be about a stone less and be in the healthy range or just over a stone more. I've been at both ends of the scale, tbh the very lowest end of the scale probably wasn't healthy and I didn't have periods, and i was at the highest end of the scale at the very end of pregnancy. I think for my frame I could probably be half a stone lighter , or slightly heavier but I don't think I'd look or feel healthy at the very outer limits either way. But I imagine it is a (fairly wide) range to allow for different builds and body shapes.

First of all don't believe everything "influencers" tell you... Secondly, the odd outlier doesn't make it ineffective as a blunt tool for 99% of us.

I don't think anybody is saying that some people in the overweight category can't be healthy. They are saying that it is unusual for the average person to have so much muscle that bmi doesn't work for them. It's literally this woman's job to be fit, her body is her business, the average person doesn't have a body like hers, that's the point of 'fitness influencers' isn't it? They are supposed to be aspirational, if her body was average she wouldn't be doing much fitness influencing.

I don’t think anyone should trust an influencer. A lot of them have been exposed for having cosmetic procedures. You also don’t know what performance enhancers they use.