Obtained from here. Not sure how accurate it is, but anyway...

A 17 year and 11 months old (female) child who is 160 pounds and is 5 feet and 4 inches tall has a body mass index of 27.5, which is at the 90th percentile, and would indicate that your child is at risk of becoming overweight.

Your child's ideal body weight would be at a BMI at the 85th percentile or below, and so would be about 149 pounds.

Remember, a child is considered to be:

* overweight if they have a BMI over the 95th percentile for their age

* at risk of becoming overweight if they have a BMI between the 85th and 95th percentile for their age

* underweight if they have a BMI under the 5th percentile for their age

And a child has a healthy BMI if it is between the 5th and 85th percentile.

Of course, this probably doesn't apply to somebody who isn't human.