http://www.livestrong.com/article/194320-body-fat-percentage-for-children/

To calculate BMI, divide your child's weight in pounds by height in inches squared, and multiply that quantity by a conversion factor of 703. The results can then be compared using the Center for Disease Control BMI-for-age growth charts for children ages 2 to 19.

http://www.cdc.gov/growthcharts/data/set3/chart-16.pdf

I agree doctors don't pay enough attention to skinny kids. They are just happy they are not obese.

I have a tween boy who is very active and an athlete.

I have talked to a few moms with the same issue and we are all suplementing with Ensure.

I also have taken some tips from runner's magazine on how to fuel and active body. You may want to check out their website.

High calorie foods like: Gu, full fat yogurt, full fat milk, real butter, nuts, granola, ice cream, cheese, cereal as a snack....
It's not the best thing in the world but Chipotle is a great way to get a lot of calories in a diet.

funny my oldest - very healthy eater, doesn't like sweets, hates anything with bubbles (soda), only drinks water,
2nd child - pasta, would love to have soda all the time - but only gets is now and then, and loves candy. (he is also skinny - just not as skinny)

Anonymous wrote:BMI isn't accurate for children. Use the height/weight charts. She is at the 30th-50th percentile - completely normal.

Right, but my question was about body fat, not BMI. I have read that too low of a body fat percentage can cause problems with puberty and possibly brain function. PP's child has a body fat percentage of 10%, which she says is ok. DH had a body fat percentage of under 6% when he was a teen, and I wanted to know if I should be worried about DD's going that low or how I could tell if it was too low. PP assured me DD is not too low just because she is so lean.

If you think about it, if DD is 50% for height but 34% for weight, and she is very muscular, she has very little body fat. If you have muscle that is the same volume as fat, muscle weighs more. The question was what is too low body fat-wise. PP assuaged my concern.

BMI isn't accurate for children. Use the height/weight charts. She is at the 30th-50th percentile - completely normal.

Thanks PP at 9:57. She is almost 11, no signs of early puberty (just a few small signs of on-time puberty; ped says we are two years away). She eats very "clean", even more so than me and my younger child. She often can be hungry so she eats when she needs to, and I tell her she can eat whatever she wants (unlike the little one who would live on pasta, Coca-Cola and chocolate if I let her!). She says her favorite food is kale.

She is a very active competitive athlete year round in one sport, does a second sport less seriously during the school year, and just finished a stint on a summer swim team, so she is burning lots and lots of calories every day. She also has that energy you mentioned. Your story helps me think that while she may not be typical of girls her age she is most definitely normal for a competitive athlete. Thanks for the reality check!

I thought BMI isn't accurate for children?

How old is your tween? Is she very active / does she participate in a lot of sports? How is her eating? Are you concerned that she isn't eating enough or enough of the right stuff?

My 9 year old has a BMI around the 10th percentile. The pediatrician has been fine with this, as DD's height / weight proportion and general leanness has been consistent all her life. She seems to take after the lean side of the family (my husband's!) The reason I go with what the pedi says is that my daughter has a lot of energy and has been able to participate in sports without problems. In fact, when it's the season for her favorite sport and her physicial activity goes up, I notice more definition in her muscles.

The overall picture doesn't worry me - DD seems to have a healthy appetite and a healthy body image. I'm also thrilled that she doesn't look to be at risk for early puberty, which can happen if the body fat percentage is too high.

Ask the doc again.

My tween has a BMI in the healthy range (16.6, which is 36th percentile), but has a lower weight percentile than she does height. In other words, her height is at 50%, while her weight is at 34% on those growth charts.

The BMI calculator said it isn't accurate if you are very muscular, which she is, but not in a bulky way. She is in a competitive sport and is very lean.

She isn't anorexic or anything, but I wonder whether there is a point where her body fat percentage could get too low? I worry about it messing with her hormones or causing some other problem. She doesn't diet. It's just that when I can see every muscle in her shoulders, I start to worry that maybe I should push her to eat more.

Does anybody have any experience with this or know whether there are resources out there where I can find out about this? The pediatrician said she was "great" at her last check up, but she has gotten even leaner since then.