How Does the Growth Chart Determine the Weight Category for My Child?
For children older than 2 years old the body mass index (BMI) is calculated using your child's height to weight ratio. It is the best standard available for defining measurements that classify as underweight, overweight or obese. This is the exact calculation:
BMI = body weight (kg) ÷ height (meters) squared
BMI varies with age, gender, and pubertal stage, so growth standards are based on BMI percentiles. The calculated BMI is plotted on a BMI reference chart to determine the BMI percentile. There are different growth charts for males and females. All children older than two years should have their BMI calculated at least annually from measured height and weight. This is done so your pediatrician can watch the trend of your child's weight over time.These are the weight categories pediatricians typically use:
- Underweight – BMI is less than 5th percentile for age and sex.
- Normal weight – BMI is between the 5th and the 85th percentile for age and sex.
- Overweight – BMI is between the 85th and 95th percentile for age and sex.
- Obese – BMI is greater than the 95th percentile for age and sex.
- Severe obesity – BMI is greater than 120 percent of the 95th percentile values or BMI is greater than 35 kg/m2 (whichever is lower)
For children less than 2 years old, we look at the weight-for-length ratio, (also called weight-for-height). A weight-for-length between the 2nd and 98th percentile reflects normal variation, whereas a weight-for-length less than the 2nd percentile may indicate undernutrition. Poor weight gain is also considered if there is a rate of weight change demonstrated by a decrease of two or more major percentile lines over time (eg, from 75th to 25th).Rapid increases in weight-for-length from zero to six months of age are associated with an increased risk of obesity at age three years. Similarly, crossing 2 or more major weight-for-length percentiles (eg, 10th, 25th, 50th, 75th, 90th) before two years of age is associated with increased risk of obesity at age five years.
If My Child Falls into the Overweight, Obese, or Severe Obesity Category, What Do I Do?
A thorough investigation with your Pediatrician is necessary to determine the cause of your child being overweight in order to best identify a way to improve your child's health. The evaluation includes a complete history, where you review everything going on in your child's life at home and outside of the home. This includes daily routines, physical activity, and eating habits of your child and family as a whole. Your doctor will also do a physical examination. Laboratory and radiologic studies also may be obtained, as needed based on the history and examination.
A Few Simple Steps You Can Start with at Home:
- Start a food log and record all the items your child eats throughout the week to better understand his or her intake
- Be an observer of the behaviors demonstrated around food and meal times.
- Give healthy calories and not sugar-packed snacks. The best food choices are unprocessed foods, such as vegetables and fruits.
Why is This important?
There may be several reasons for your child being overweight. It is very important to rule out a physiologic underlying cause. Once that is ruled out, a balanced diet and daily physical activity are they key to children maintaining good health all their lives and avoiding the morbidities that being overweight and obese cause, such as diabetes. You are setting the stage now for how they will live their lives and shaping the choices they will make for their future.