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Original poster

NHS bmi

63 replies

MarthaMayWho · 09/12/2023 22:41

I was well versed on the NHS Bmi. You used to have to put in male or female and your ethnicity. Changing the sex used to massively skew whether you were in the health zone or not.

NHS bmi tool now has no option to choose sex so now a blanket bmi.

Surely this is going to cause problems?

OP posts:
MilkChocolateCookie · 10/12/2023 07:51

Yes - that's because BMI is defined differently for under 18s. But for adults it's the same calculation isn't it?

bmiIsDefined · 10/12/2023 07:50

MilkChocolateCookie · 10/12/2023 07:28

I don't see why it matters? It's the same calculation for men and women isn't it?

Yes, and nothing about the thresholds (underweight below 18.5, normal 18.5-25, overweight 25-30, obese over 30) has changed from what I'm used to seeing either (I only checked for white ethnicity - there's an argument for Asian ethnicities having different thresholds but I don't know details and wouldn't know if that has changed). Maybe (if they've really changed the calculator) the new thing is that they used to ask for sex and then do nothing with it, and now they don't ask? I have no explanation for the people above who say their actual results have changed though.

Ereshkigalangcleg · 10/12/2023 07:47

BMI calculators definitely used to commonly ask for sex to be able to tell you whether the BMI is in the normal range or obese etc (which sex is often relevant to). The NHS calculator still does ask for young children and teenagers.

A child or teenager's BMI is shown as a "centile". The centile result is shown as a percentage of how their BMI compares with other children or teenagers of the same age and sex.

Sex

Please enter sex
Why are we asking?
For children and teenagers, BMI centile is sex specific. We give more personalised information based on whether you are male or female.

https://www.nhs.uk/health-assessment-tools/calculate-your-body-mass-index/calculate-bmi-for-children-teenagers/

MilkChocolateCookie · 10/12/2023 07:28

I don't see why it matters? It's the same calculation for men and women isn't it?

Quiregirl · 10/12/2023 07:10

Bingo!
Page last reviewed: 28 November 2023

Quiregirl · 10/12/2023 07:09

It's changed, and very recently I'd say. I check my BMI using this tool and last did so a couple of weeks ago. It has ALWAYS asked for sex and provided a clickable link to 'why do we ask this' information for the question.

bmiIsDefined · 10/12/2023 01:22

This seems a bit confused. BMI is defined, and always has been, as the person's mass in kilograms divided by the square of their height in metres. If anywhere is giving a number that is different for people of different sexes/ethnicities/gender/eye colours, then whatever that number is, it isn't BMI. It could be that different sites use different cut-offs for what they consider healthy, based on those things, though - is that what you mean, OP? What's the page you're looking at? The easily found NHS BMI calculator seems to be this one, which I don't think has changed much in a long time. It doesn't ask for sex (or gender) but I don't think it ever did.

www.nhs.uk/health-assessment-tools/calculate-your-body-mass-index/calculate-bmi-for-adults

CervixSampler · 10/12/2023 00:50

My BMI is unchanged as expected but I don't like that they've changed it. I tried clicking on the survey option but it's not available Hmm

PomegranateOfPersephone · 10/12/2023 00:33

Just checked this out and on the NHS calculator I am now 1.1 BMI points higher than on a health app which uses sex. NHS asks ethnicity but not sex.

ChristmasPuddy · 10/12/2023 00:25

It’s based on one chart so I don’t see how it makes a difference?

NeighbourhoodWatchPotholeDivision · 10/12/2023 00:11

I swear that the healthy range for my own height has been changed by this! It used to be a kilogram higher!

Original poster
MarthaMayWho · 09/12/2023 23:17

I like bmi. Like you say, women have a natural range of sizes and my natural waist is huge (even when I was underweight and had an eating disorder I registered as 'fat' according to waist measurements.
Bmi worked for me, gave me an achievable goal when I had to lose baby weight as it would subtly change with each kg. Waist size doesn't do that.

Just because it is not accurate for some people doesn't mean it's ok to make it less accurate for women.

OP posts:
Fenlandia · 09/12/2023 23:10

BMI is a nonsense metric anyway, I'm surprised the NHS is still using it. Women in particular have a huge range of body shapes and composition due to breasts and hips

(https://www.medicalnewstoday.com/articles/265215#Waist-size-linked-to-diabetes-risk,-regardless-of-BMI)

As the link says, waist size is a much better guide to people's health risks than a metric designed by a 19th century Belgian mathematician who was literally trying to find out the "average man" - not invent a health measure.

Why BMI is inaccurate and misleading

Body Mass Index (BMI) is not a very accurate measurement for determining whether somebody is of normal weight, overweight or obese, researchers say.

https://www.medicalnewstoday.com/articles/265215#Waist-size-linked-to-diabetes-risk,-regardless-of-BMI