Signs Your Child is Underweight (ages 5 to 8)

How can I tell if my child is too skinny?

There are several factors to take into consideration when evaluating your child’s weight. Has he always been thin? Are both of his parents very thin? A child who has a genetic tendency to be thin is in a different boat than a child who has always been normal to hefty and who has recently stopped gaining — or started losing — weight. Even if your child has just recently thinned out, though, there may be nothing to worry about.

“Keep in mind that a child’s weight is dynamic and changes with growth,” says Stephen R. Daniels, M.D., Ph.D., a professor of pediatrics at Children’s Hospital Medical Center in Cincinnati and a member of the American Academy of Pediatrics committee on nutrition.

When an increase in height precedes a gain in weight, Daniels explains, your child may appear underweight for a while, until his weight gain catches up. It’s also possible, though, for your child’s weight gain to eventually outstrip his gain in height, resulting in his becoming overweight. Doctors are very concerned that many children are becoming overweight as they grow older, Daniels says, and some of those children started out as underweight.

The best way to determine whether your child is underweight — and to find out what to do about it — is to make an appointment with his doctor so she can help you evaluate his weight and his diet.

How will the doctor determine whether my child is underweight?

Your child’s doctor will take into consideration the factors mentioned above — how much his parents weigh and how long he’s been thin. She’ll also evaluate your child’s eating habits and his overall health. She’ll probably ask if your child has had any medical problems that may have contributed to weight loss, like chronic diarrhea or vomiting.

The doctor will measure your child’s height and weight and plot these numbers on a growth chart. Doctors today are using a new series of growth charts from the Centers for Disease Control and Prevention that take into consideration a child’s body mass index, or BMI, which considers weight together with height to help determine whether they are proportional. The BMI is a better indicator of body composition than a weight measurement alone. While an adult’s BMI is calculated with a straight formula of height and weight, the formula to determine a child’s BMI takes into consideration gender and age as well, to allow for the fact that body composition changes as a child gets older.

If your child’s BMI falls below the 5th percentile, he’s considered underweight. The doctor will ask you questions about your child’s diet, so she can pinpoint any major deficiencies. She may have you refer to the Food Guide Pyramid, so you can determine which food groups your child may not be getting enough of. She’ll do a physical examination and may run laboratory tests to determine if there’s an underlying medical cause, especially if your child seems to be eating well but not gaining weight.


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