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Medical Author:

Robert Ferry Jr., MD

Robert Ferry Jr., MD

Robert Ferry Jr., MD, is a U.S. board-certified Pediatric Endocrinologist. After taking his baccalaureate degree from Yale College, receiving his doctoral degree and residency training in pediatrics at University of Texas Health Science Center at San Antonio (UTHSCSA), he completed fellowship training in pediatric endocrinology at The Children's Hospital of Philadelphia.

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Medical Editor:

Melissa Conrad Stöppler, MD, Chief Medical Editor

Melissa Conrad Stöppler, MD, Chief Medical Editor

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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Weight-to-height tables

These tables give general ranges of healthy weight and define being overweight based on the height of the child or teenager. Many health care professionals define obesity in a child as weighing 20% or more over the healthy range. The tables, however, do not take into account other individual characteristics of each child or teenager. The health care professional must consider the patient's age, gender, pubertal stage, and growth pattern when interpreting the weight-to-height chart. For example, some children gain weight before a growth spurt. This does not necessarily mean they are becoming obese.

Body fat percentage

The percentage of body weight that is fat is a good marker of obesity. Boys with over 25% fat and girls with over 32% fat are considered obese.

Body fat percentage is difficult to measure accurately. The most accurate methods use special equipment not found at most medical offices. The method that measures skin-fold thickness is unreliable unless performed correctly by a trained and experienced technician.

Body mass index (BMI)

This measure assesses weight relative to height. It is the same as the body mass index used to identify adult obesity. BMI is defined as weight (in kilograms) divided by height (in meters) squared (kg/m²). Less commonly, BMI can be calculated in pounds and inches. BMI is closely related to body fat percentage but much easier to measure.

BMI is the standard for defining obesity in adults, but its use in children is not universal. The Centers for Disease Control and Prevention (CDC) suggests two levels of concern for children based on the BMI-for-age charts.

1. At the 85th percentile and above, children are "at risk for overweight."
2. At the 95th percentile or above, they are "overweight."

The American Obesity Association defines those children and adolescents above the 95%ile as "obese," which corresponds to a BMI of 30 kg/m² (considered obesity in adults).

To calculate a child's BMI, follow these steps:

1. Multiply the child's weight in pounds by 705.
2. Then divide by the child's height (in inches).
3. Divide this again by the height (in inches) again.

To calculate BMI via the Internet, enter the child's height and weight at the web site of the Department of Health and Human Services, Obesity Education Initiative.

Waist circumference (WC)

This measurement in a child or adolescent correlates closely with the future risk of developing type 2 diabetes mellitus and related complications of the metabolic syndrome (high blood pressure, abnormal cholesterol or other fat levels, heart attack, stroke, and damage to eyes, heart, and kidneys). The assessment is made with a tape measure stretched across the widest abdominal girth (usually at or just below the level of the belly button, called the umbilicus). Any value over the 90% percentile for age and gender carries the highest risk.

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