why doesn't BMI work for athletes?

[KatyMac]

I mean I know it's to do with density of muscle vs fat

& I know it should be viewed with caution

But DD (16) is concerned as she thinks hers is high I'm concerned as I think her weight is low but it's because she does 16+ hours a week high impact dance (imo) that has made her more muscled and warped the result

But is there a good website to read that explains it rather than it being "well mum said..."

What is her height and weight? BMI doesn't take into account fat percentage, which I think I remember reading should be 20% for a non athlete. Are any of the NHS websites any good?

BMI is crap.

DH ran a marathon. BMI said he was seriously obese at the time.

Many top rugby players would be classed as obese too.

Not really the NHS site is a bit woolly for teenagers and nothing much about muscle

She is 5ft 4 & 8 stone - which sounds fine but she is very thin (34, 24, 34) which isn't reflected in the BMI which is about 19 which implies she is mid range rather than low

Was she the dancer you posted video of? She did not look like someone who has a high BMI! Could you find out how many calories one dance session burns? (This might make her realise how much fuel she needs.)
FWIW my petite fitness instructor weighs over 12 stone. Hardly an ounce of fat on her. She is incredibly fit but muscular.

tbf this nhs page says "Muscle weighs more than fat. Very muscular people, such as heavyweight boxers, weight trainers and athletes, may be a healthy weight even though their BMI is classed as obese"

It isn't high, she believes it's high

My word isn't good enough as I'll say anything; so I need something reputable

BMI doesn't work on teens and kids (different muscle/fat to height to adults), she needs to use a pediatric BMI calculator. I doubt her level of exercise skews it past the point of normal, you need to be bulky (eg rugby player as a pp said) for it to be really wrong.

And it's only about averages as well - being skinny doesn't automatically mean a low BMI within the normal range.

Also 19 is not a mid range BMI? 18-25 is "normal"...

But it isn't much is it?

She has been on a weight loss website tonight & it's saying she is middle of OK - so she needs to carry on being careful with what she eats......she doesn't

she's on something like the 25th centile if you use the teen one (which I am trying to persuade her to use) a year ago she was on about 11th so it is getting better

I don't want her to think she needs to eat carefully or risk putting on weight - I want her to think she should eat a healthy full diet to maintain her weight and maybe put on a little

"some people, such as heavily muscled athletes, may have a high BMI even though they don't have a high percentage of body fat."

A 24 inch waist is in no way shape or form overweight. I'll look for some info on that...

Honestly I think the best thing to do is get to the bottom of why she thinks of weight as a target in the first place rather than getting into the finer points of BMI. The problem with that kind of mentality is the number will keep fluctuating - during each day, during each hormonal cycle, after a lot of exercise etc. To a large extent it's irrelevant what the scales say as long as your jeans still fit you. Obsessive weight focus is a bit of a red flag for developing an eating disorder...

That has a bit more info 13Stitches

She thinks she is on the heavy side of 'normal' and I want her to understand she is on the very light side of 'normal' & being a bit heavier would be good/OK

It doesn't work because it doesn't look at how much body fat you carry, which is Thr health issue.

It only counts total weight. It's a very blunt tool.

This might help if your dd would have a look...

www.dietandfitnesstoday.com/bmiathletes.php

It isn't obsessive - it just pops up sometimes; a fair few of her friends are trying to lose weight some need to think about it, some don't - I'm woried about her jumoing on the bandwagon

We talk about shape & size wrt clothes (eg an age 3-4 skirt that still fits her waist) but most of her clothes are lycra!!

But a real understanding that the way weight is talked about & BMI being inaccurate will help

"You have a Waist to Hip Ratio of 0.71..."

"Female 0.80 or below Low Risk"

Also (although the site doesn't fill me with confidence): [[http://scars1.com/Care_Tools/Calculators/Advanced_BMI/Results "Recent studies*, however, indicate that the Waist to Hip Ratio (WHR) may be as good as, or a better, indicator for determining health risk than the BMI. WHR indicates weight distribution (body shape), which can be significant in your overall health. As a female, your WHR should fall under 0.78. You may want to print this report and bring it to your next visit to a physician.
Your Waist to Hip Ratio (WHR) is: 0.71"]]

I haven't got any other wise words, I'm afraid. Teenagers and body image/weight issues are a complete minefield. I'm just the google-monkey on duty!

Good luck, OP.

BMI is a very crude measure. There is a lot of evidence now that people with higher BMIs can actually be healthier than those with low ones - what really matters most is (a) where your fat is (essentially, visceral fat is bad, but fat on bum, legs, boobs and arms really isn't unless there's so much it stops you doing things to keep you fit) and (b) whether you're fit or not.

Being underweight (ie BMI below 18 for adults) is statistically much unhealthier than being in the 'overweight' category. [the numbers may be a bit different for teens but she really doesn't want to get the idea that a BMI of 19 is high!

There is a piece in todays Times which covers some of this, and there was a piece in the New Scientist a few weeks ago - not sure if you'd be able to get hold of that somehow.

Your DD has a slim waist and is clearly very fit!

Remind her that weight per se is not a problem - fat may be if its in the wrong place but that if she loses weight then (given that presumably she doesn't have much fat) she will be losing muscle - the stuff that allows her to dance.

13 & rhonda - those together should help

The ideal weight bit of rhonda's shows how little she would have to lose to become underweight - ie 4lbs

That is really significant

I agree 13 - & I lose control of her diet in a few months so I want lots of positive reinforcement before she goes

Teens are so complicated

Some of the weight/height calculators give useful ranges eg this one puts your DD in the 'extremely thin' bracket (below 'slender and healthy' but fortunately not down to 'abnormally slim to underweight).

TBH it's probably fine for a 16yo to be thinner than an adult but you're def right she doesn't need to lose weight!

I meant waist/height calculators!

That's useful too

I think knowing 4 lbs less would mean underweight is understandable & if another site suggests she is extremely thin that helps too

I think it's all about her perception