July 2021

Should You Worry if Your Child Has a Low BMI?

Body mass index (BMI) is an easy way to estimate body fat and screen for weight categories that could lead to health issues. For all ages, BMI is based on height and weight measurements. But for kids and teens, BMI is also plotted on gender- and age-based growth charts. Using these charts from the Centers for Disease Control and Prevention, pediatricians can compare BMI levels with other children at the same development stage.

The negative health effects of childhood obesity are well-known. Kids who are obese are at risk for: high blood pressure, high cholesterol, type 2 diabetes, joint problems, and other health issues. But what about kids who are underweight? 

Charting their growth

Children are considered underweight when their BMI is below the fifth percentile on the growth chart. About 4% of kids and teens in the U.S. are underweight. They could either take in fewer calories than they need, use more calories than they consume, or both. Some kids, however, are naturally thin even though they eat well and are physically active.

When to see a doctor

Talk with your child’s pediatrician if you’re concerned that your child is too thin. Or if you notice they consume enough calories but still doesn’t gain weight. The pediatrician can help find any underlying medical conditions that may be to blame.

It’s a good idea to watch for signs of potential problems. Being underweight can indicate that kids have health, emotional, or dietary issues. In addition, children who are underweight are more likely to be bullied by their peers. Victims of bullying are at risk for depression, anxiety, low self-esteem, and other issues that affect their mental and physical health.

Helping your child thrive

Keeping your child’s BMI in the healthy range is important for their overall health and well-being. If your child is underweight, the pediatrician can help you develop good habits at home.

When weight gain is recommended, here are some ways you can help your child add pounds:

  • Prepare nutritious, higher-calorie meals and snacks. Focus on protein, carbohydrates, and healthy fats.

  • Have your child assist with planning meals, food shopping, and preparing meals to spark an interest in eating and food.

  • Make mealtimes fun and relaxed! Kids shouldn’t feel rushed to finish eating.

  • Teach your child not to fill up on beverages, such as juice and milk, so that he or she still has an appetite for dinner.




Date Last Reviewed: 3/1/2021
© 2000-2022 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.