Falling off the growth curve indicates a serious medical problem. Most kids have a growth curve chart in their medical file. At each doctor visit, height and weight is measured from birth till age 20. In healthy children height and weight increases along a fairly constant growth curve. When a child falls below his or her previously established growth curve, an investigation into the cause should be undertaken. Besides an eating disorder, falling off the growth curve may indicate the onset of a chronic illness such as inflammatory bowel disease or a food allergy.

Age and gender have a significant effect on weight in growing kids so height and weights are recorded on growth charts as BMI age—and gender-specific percentiles. Kids who are on the 50th percentile are likely to be developing just fine. A child below the 25th percentile may be underweight; a child above the 95th percentile maybe overweight.  But if a child has always tracked on the 25th percentile chances, he or she is just fine. Same goes for a child who has always been at the 95th percentile. The most important issue is whether the child is staying on his or hers established growth curve.

Besides assessing whether a child is growing and developing as is predicted by their growth curve, other important indicators of normal development in girls and boys are age-appropriate menstrual physiology and in boys, it is physical signs of sexual development and expected growth in height. In girls, however, height growth is delayed during the pubertal weight gain period. We have seen patients and/or their parents often wrongly interpreted this normal change in weight in girls as excess weight gain. Click here to download a growth chart for your boy or girl.

In children and adolescents with eating disorders, a minimum safe weight is consistent with each child’s growth curve or at least the 25th percentile. Anorexia in children and adolescents is usually defined as weights below the 5th percentile. Click here for an example of what it looks like when a child falls off their growth curve. To calculate your child’s BMI percentile click here.

I’ve talked in a past blog about the problem created by current adult BMI categories which are based on World Health Organization’s (WHO) data for healthy weights for adults living in Asia. In Americans, these categories minimize the dangers of low weights and exaggerate the dangers of higher weights. Though I am happy to report that the official (from the CDC) percentile categories for children two to 20 years old are derived from studies of American children, in my mind, these categories also minimize the dangers of low weights and exaggerate the dangers of higher weights in children. Ironically, WHO adopted and uses the US-derived percentiles as its worldwide growth standards for children and adolescents.

Here are the current US BMI percentile weight categories for children up to age 20:

Weight Status Category

Percentile Range


Less than the 5th percentile

Healthy weight

5th percentile to less than the 85th percentile


85th to less than the 95th percentile


Equal to or greater than the 95th percentile

I prefer the following BMI categories because they are consistent with research findings. I use them in my practice for children and adolescents.

Weight Status Category

Percentile Range

Risky Low Weight

Less than the 5th percentile

Low Weight

5th percentile to less than the 25th percentile

Safe Weights

25th percentile to less than the 85th percentile

Heavier Weight

85th to less than the 95th percentile

Possibly Risky High Weight

Equal to or greater than the 95th percentile

My take home message about assessing a safe and biologically appropriate weight for children and adolescents is to look for BMI percentiles between the 25th percentile and the 85th percentile that are consistent with each child’s growth curve. If your child is outside these ranges or they have fallen off or gone above their growth curve, consult with your pediatrician.

Nutritionist Marcia Herrin and Nancy Matsumoto, co-authors of The Parent’s Guide to Eating Disorders, Gūrze Books. Marcia is also author the soon to be published Nutrition Counseling in the Treatment of Eating Disorders (September, 2012). Read more from Marcia and Nancy by clicking here.

Copyrighted by Marcia Herrin and Nancy Matsumoto

About the Authors

Marcia Herrin, Ed.D., M.P.H., R.D.

Marcia Herrin, Ed.D., M.P.H., R.D., is the founder of Dartmouth College's nationally renowned nutrition programs. Currently, Dr. Herrin conducts a private practice in Lebanon, NH.

Nancy Matsumoto

Nancy Matsumoto is a freelance journalist who has written numerous stories on health, eating disorders, and body image.

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