What Parents Should Know About BMI

February 2023

As a parent, you probably think a lot about keeping your child safe. Helmets and knee pads can help protect them from bumps and bruises. Vaccines shield them from serious diseases. But there’s another important way you can safeguard their well-being: helping them maintain a healthy weight.

Childhood obesity has become an epidemic. And it starts early—right now, about one in five kindergarteners already carries extra pounds.

A red flag for health problems

Being overweight or obese can cause problems for kids. Sometimes, they will have mental health issues, such as anxiety and depression. They may also be targeted by bullies.

Children with obesity may develop physical health problems, too. These issues can start when they are young or develop as they get older. They include:

• Diabetes

• More severe COVID-19 infection

• High blood pressure and cholesterol

• Heart disease

• Joint pain

• Sleep apnea

• Asthma

Being underweight is also dangerous. It can cause problems such as malnutrition and weak bones, or lead to an eating disorder.

Measuring up

To protect your child’s health, it can be helpful to understand body mass index (BMI).

This is a measure of weight based on height. The pediatrician will check your child’s BMI at regular visits beginning at age 2. They will weigh your child and measure how tall they are. Then, they’ll compare your child’s BMI with other kids who are the same sex and age.

Usually, you will get a number called a percentile. If your child is in the 85th to 94th percentile, they are generally considered overweight. At or above the 95th percentile is obese, with the higher end of the range being considered severely obese. If they are below the 5th percentile, they are likely underweight. Ask the pediatrician to explain your child’s numbers and what they mean.

What’s affecting the numbers?

Reasons some children have a higher BMI than others include:

• The foods that fuel them. Many kids do not get enough vegetables, fruits, or whole grains. They may also consume larger portions than needed.

• Sitting still. Children should move for about an hour each day. But only about one in four does. If you live in an area where there are not many parks or sidewalks, it may be harder for kids to stay active.

• Subpar slumber. Not getting enough rest may lead to obesity.

• Mean genes. Sometimes, obesity runs in families. It may be naturally easier for your child to gain weight, or harder to lose it.

Get the big picture

BMI is just one measure of your child’s weight and health. And it does not always provide an accurate snapshot.

Here’s one example: Any child with a BMI greater than the 85th percentile is classified as overweight. But a young athlete might have a BMI in that range because they have a lot of muscle rather than body fat.

Talk with your child’s pediatrician if you have any concerns about their weight. They will consider your child’s build and lifestyle and advise you on adopting healthier habits at home.