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To wonder what's the point of the BMI system?

20 replies

Tminus3days · 20/11/2019 08:41

I'm on the lower end of the BMI scale (19.2). If I put my weight and height into the online NHS calculator it says that I'm on the lower end and should chat to a doctor as my diet my not be giving me enough calories. What is the point of the BMI scale if it tries to send you to waste the GP's time when you're still within it's range??

OP posts:

SerenDippitty · 20/11/2019 08:46

Because you should only be at the lower end if you have an exceptionally small frame/light build. That’s why it’s a range. You could technically be a healthy weight for your height sbut under/overweight for your frame/build.


Camomila · 20/11/2019 08:50

I guess because it's right at the bottom of 'normal' and not a lot of people in the UK have a BMI of 19 naturally?

I think you can use your common sense though, my BMI is 19 and I'm pregnant and no one is worried about it...but I'm a 5'3" Italian lady with tiny hands and feet, its clearly just my normal frame.

I do wonder how well BMI works across ethnicities though and if ordinary people know there are some variations. DH is East Asian and apparently shouldn't let his BMI go above 23 (due to the increased diabetes risk)


Camomila · 20/11/2019 08:54

It's not 19 now! I meant at the booking in appointment. I've had hyperemisis so my weights been asked about more than usual I think.


Tminus3days · 20/11/2019 11:33

I'm 5 ft and have a really small frame, I work out a lot and try to limit my intake of unhealthy food, don't drink alcohol etc. I think there are a lot of people the BMI doesnt work for. Two years ago I had a BMI of 24, so technically healthy. But even when I got down to 22 I still look very overweight!

OP posts:

soulrunner · 20/11/2019 11:36

Jonny Wilkinson. There, said it so no-one else has to.


araiwa · 20/11/2019 11:42

It was invented by the nhs to generate threads on aibu

Its a pretty simple to understand system that could higlight an issue that requies further checks or research. Its not perfect but it does a decent job roughly for most people


awesomeaircraft · 20/11/2019 11:45

Because at the end of the day we need a general yardstick to measure health parameters among a disparate population and the granularity happens later on.

And yes, sending the outliers to the GP is expensive but missing out on a condition is also expensive to the NHS in later on care.


awesomeaircraft · 20/11/2019 11:46

It was invented by the nhs to generate threads on aibu or that Grin


PurpleDaisies · 20/11/2019 11:47

These threads often attract people with disordered eating.


Everanewbie · 20/11/2019 11:50

My opinion is that BMI provides a decent overview of where your weight should be according to your height. It isn't meant to be absolute and doesn't work so well for certain body types. As a PP said, Johnny Wilkinson. But people are quick to use this to justify a BMI result they don't like. You have to be pretty damn muscly, i.e. prop forward/weight lifter/ body builder to be an exception on these grounds. 99% are, dare I say, just overweight and slightly in denial.


Aroundtheworldin80moves · 20/11/2019 11:55

When DD1 was a baby at weighing clinic, HV plotted her centiles- which showed her to be worryingly underweight (as length centile much higher than weight). However a quick look at her revealed actual story- she was a skinny baby, but with very long legs. Her (child) BMI now is a similar situation, it looks low but she still has disproportionately long legs. However it's an indicator of a problem.


soulrunner · 20/11/2019 12:01

ever quite- my JW comment was precisely because everyone uses professional sportspeople as reasons why bmi is ‘rubbish’ when in fact most pro sportspeople have a BMI in the normal range. If muscle was the reason why the average bmi has increased so much, where are all the super jacked people? And of course, having a lot of muscle and being ‘over fat’ are by no means mutually exclusive.


ComtesseDeSpair · 20/11/2019 12:02

If you are just on the cusp of “healthy” at either end, you should probably attention to your diet and exercise to make sure you stay thy way and don’t cross the line. If your weight is consistent and you don’t fluctuate, you’re fine.

BMI works for the majority of people - yes, even super fit muscular people for the most part. Both my (male and female) personal trainers are competitive weightlifters and even they fall into a “healthy” BMI, albeit right at the top limit. As a previous poster said, people who don’t like what their BMI tells them are pretty much always making excuses.


horse4course · 20/11/2019 12:07

I think unless people have a psychological issue, you can tell if you're too fat or too thin.

The history of BMI is quite interesting, they've moved the parameters a couple of times so people would have been healthy weight one day and overweight the next!

The other issue is the near impossibility of losing weight and keeping it off when you've got properly big. Much better to emphasise nutrition imho. Focus on weight encourages self loathing.


Tminus3days · 20/11/2019 12:08

I'm personally not making excuses for anything. My weight has been stable at 7 stone for almost 2 months. It occasionally goes up by a couple of pounds, it's only ever gone down to 6 st 13.5 lbs.

I can see how some people can make excuses especially when at the higher end of the scale though.

OP posts:

Glitterbaby17 · 20/11/2019 12:23

It’s an interesting one and I think that more people’s healthy ranges fall ‘outside’ the range dictated by BMI than some people like to thing. I’m moderately active (exercise 3-4 times a week) and was very sporty when I was younger. I got a body fat test done as I was having a big fitness push and the healthy range for me based on body fat percentage was 6kgs heavier at both ends than BMI. Body fat is a better indicator, but the crappy scales often get it right so you need to get it done properly.


Pinkflipflop85 · 20/11/2019 12:30

BMI was not invented by the NHS. It was devised by a Belgian mathematician in 1830.


Disquieted1 · 20/11/2019 12:30

Maybe BMI has done more harm than good. Those at the extremes know the situation already. I just wonder how many millions of people have been caused angst, worry even stress over a few kilos here or there.


PhoneLock · 20/11/2019 12:36

I'm right at the lowest edge of the range get the same message if I use the NHS BMI calculator. I understand why it is there. There could be an underlying health issue, particularly if the reading is the result of recent unexplained weight loss.


NaviSprite · 20/11/2019 13:29

This might be an interesting read regarding BMI and whether - by today’s standards, it is too simple a formula to truly calculate body fat ratios:

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