Body Mass Index in Children: Care Instructions

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Starting when your child is age 2, the doctor will calculate your child's body mass index (BMI). BMI helps the doctor track a steady rate of growth. It's just one tool to see if your child may be under– or overweight.

BMI is based on your child's height and weight. These measurements give you your child's percentile on a growth chart. The percentile is the number that compares your child's BMI to other children of the same age and sex. There are four BMI categories for children.

  • A BMI of less than the 5th percentile is considered underweight.
  • A BMI in the 5th to 84th percentile is considered a healthy weight.
  • A BMI in the 85th to 94th percentile is considered overweight.
  • A BMI in the 95th percentile and above is considered obese.

If your child's BMI is a concern, your doctor may ask about your child's diet, activity, or family history. The doctor may order tests to look for other health problems. He or she may also want to do a skinfold test. This test measures the thickness of fat at one or more places on your child's body.

Children who are in the:

  • Underweight range may have a risk of not getting enough nutrients. They may also have a higher risk of being overweight later in childhood.
  • Healthy weight range may have a lower risk of health problems.
  • Overweight or obese range may have a higher risk of health or social problems. These can include high blood pressure, diabetes, stress, and low self-esteem.

Follow-up care is a key part of your child's treatment and safety. Be sure to make and go to all appointments, and call your doctor if your child is having problems. It's also a good idea to know your child's test results and keep a list of the medicines your child takes.

How can you care for your child at home?

If your child is in the underweight BMI range

  • Focus on whole foods that provide energy and are high in nutrients.
  • Include healthy fats (like avocado, nuts, and olive oil), cheese, and cream.
  • Work with your doctor or dietitian to make a plan.

If your child is in the overweight or obese BMI range

  • Focus on whole foods, including fruits, vegetables, whole grains, lean protein, and low-fat dairy.
  • Work with your child on portion sizes. An easy way to start is to make sure that half of the foods on your child's plate are fruits and vegetables.
  • Encourage your child to be active every day.
  • Work with your doctor or dietitian to make a plan.

To help your child form healthy habits for life

  • Eat together as a family as much as you can. Offer everyone the same food choices.
  • Limit sweet drinks. Encourage your child to drink water when he or she is thirsty.
  • Avoid power struggles. Your job is to provide healthy choices. It's your child's job to choose to eat or not eat.
  • Avoid using food as a reward, whether for an achievement or for "eating all your green beans." (The "nutritious food, then dessert" tactic makes healthier food seem less desirable.)
  • Be a role model. Even if you struggle with how you feel about your body, avoid talk about "being fat" and "needing to diet." Instead, talk about and make the same healthy choices you'd like for your child.
  • Get help. If your child is a picky eater or struggles with body image, talk to your child's doctor. The doctor may have resources that can help.

Where can you learn more?

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The Health Encyclopedia contains general health information. Not all treatments or services described are covered benefits for Kaiser Permanente members or offered as services by Kaiser Permanente. For a list of covered benefits, please refer to your Evidence of Coverage or Summary Plan Description. For recommended treatments, please consult with your health care provider.