14 year old dd is underweight on the BMI calculator

[Tonylepony]

I’ve not thought about dd’s weight since she was a toddler. She’s always been slim and from being small was around 90th percentile height and 50th percentile weight. We regularly measure our dcs height and draw a line on the wall just to see how much they’ve grown but we never weigh them. Last night dd told me she was underweight. She’d been on the scales and then entered her height and weight on the NHS BMI calculator as it’s something they’re doing at school. I checked and she is in the red zone as being underweight. She’s 168cm and weighs 7 stone 11lb. She looks perfectly healthy to me, has regular periods, eats well but is good at self regulating - if she’s eaten loads for lunch she won’t have a big tea etc. She’s always been like this. I’m a bit shocked really and not sure whether this is ok or not. I’ve heard plenty about overweight dc but not about them being underweight unless there’s eating issues which is not the case here.

I get you, DS is underweight too and I always panic slightly if he gets ill (with stomach bug or something like that) because he is so slim. I try to boost his food with full fat yogurt, cream, butter, and make sure he has good snacks. He eats ok, just small-ish portions. You can mention it to your GP

My DD was similar at 12/13 - she was going through massive growth spurts at the time and it seemed she just couldn't eat enough to stay a healthy weight - as the spurts slowed down she balanced out again and is now at 14 a healthy (though bottom end where she has sat naturally most of her life) size 6.

I mentioned it in passing to a doctor friend of mine who said not to worry as they don't use BMI with teens as it just isn't useful at that point.

I think your instinct is right that it's not a problem. I am 162 cm and as a teen into early 20s I was 7 to 8 stone. No eating or health issues. I am very small framed though and these charts don't take that into account.

This sounds like my DD. I don't worry. The reality is she's going to change throughout her adolescence; she's grown rapidly in the past year so is tall & skinny at the moment. It'll even out tho I expect she'll continue to have a slim build.

Lots of teens go through skinny or chubby phases as they grow. I was whippet thin as a teen (alas no more). As long as she's happy and healthy and eating properly, I wouldn't make a big deal out of this.

You made me wonder as my DD is almost exactly the same measurements as that. I went on the NHS bmi website for children (there's a different one for adults) and she came out as fine - on the low end of the scale but fine. I wonder if your dd was looking at the adult bmi measurement site?

Thanks so much. I’ve never made a big deal about food and never forced them to clear the plate etc. Some days she’ll eat more than her brother who’s 6ft 5 other days she’s not hungry and only eats half but that’s how she’s always been.

At 14 I was already 170cm and only 7st 7-10lbs. I was skinny but healthy. Normal skinny a generation ago is now considered underweight....

My DD is just like yours OP, even the same height 😊. The advice I’ve always been given is that if they follow their line on their growth chart then no need to worry. It’s only if they go down that it can become an issue.

She’d been on the scales and then entered her height and weight on the NHS BMI calculator as it’s something they’re doing at school. I checked and she is in the red zone as being underweight. She’s 168cm and weighs 7 stone 11lb

But this is not underweight on the NHS calculator for any 14year old.

My guess is she's used the adult measure not the one appropriate to her actual age.

I was exactly like this all through my teens and early 20s. I started university at 18 years old weighing 6 and a half stone, which was the heaviest I'd ever been (though I was a lot shorter than your DD at 5 foot 1). I stayed that weight until I was about 22, and settled at 7 stone. I am much heavier now at 45!

But I was always healthy (didn't come down with many illnesses), regular periods, good exercise and mentally strong.

Please don't worry if everything else is as it should be.

Have you used the kids version?
Guessing a DoB, she comes up as ok when I've just done it on the NHS site.
And as an adult BMI, it's only just underweight. I'd guess she's perfectly healthy, but double check the figures.

164cm here and I was 7 10 when I married at 24 - that was definitely heavier than I was at your DD's age so
I think it's fine. Periods regular, played sport 6-7 times a week at school, plenty of energy for studies etc

Teenagers different to adults for bmi I think

You are using the adult calculator, she is of healthy weight for a 14 year old.

14yr old DS has always been whip thin and righr at the bottom of the BMI scale.
Like you, I worry, but I know he eats well and is quite active.

As others have said, sounds like she's using an adult calculator.

BMI is also not a useful tool really in the bigger scheme of things. If her weight is remaining stable and her growth charts are stable, that's far more important at this point. I'd be concerned if you see any signs of actual weight loss but while she might have gone through the initial part of puberty and be having periods, she's still a child and won't have a woman's extra fat reserves etc.

I was very skinny as a teenager. The only time my parents worried was when I lost weight at a time that happened to coincide with my first boyfriend. It definitely wasn't a lack of eating (the boyfriend was old fashioned and loved "taking me out" ) so can only assume it was linked to hormones or growth. Sadly, am not even vaguely skinny now.

Thanks for the discovery! I see we were looking at the adult BMI calculator. I’m actually quite relieved despite knowing deep down it wasn’t an issue.

I’m classed as underweight too in my BMI and I’m 26, but my whole family are the same. I’m definitely not underweight and your DDs weight sounds normal to me

I stopped growing (height wise!) at 13 and am the same height as your daughter. I was a similar weight to her now in my early teens but as I got my adult body I naturally put weight on and levelled out at 9st when I was about 18.

If she’s healthy and eats well etc I wouldn’t be worried - BMI is a sketchy measure of health at the best of times.

I work in a children's eating disorder service and we would not use BMI as a reliable measure at all.
If you're child is developing normally (sounds like you are seeing growth?), she has energy throughout the day and is showing no signs that she is underfed or undernourished (paleness, dark undereyes etc) then that is perfectly fine for her :)

This was me growing up (although I was even skinnier!). You're definitely right to not think of it as a big deal - as long as her eating habits and attitudes are healthy, that's that. Some people are just built much slimmer than others, and it's also very common at that age for height and weight to not be proportionally increasing. I'm still fairly underweight but my doctors have never been concerned as I've been on the same trend line since I was a toddler. Just keep encouraging healthy eating habits and she will be just fine!

Also, the fact that she came to you to tell you that she is underweight feels like a good thing to me. If there were a problem, it seems more likely that she would be trying to hide it.