Patient information from BMJ

Weight problems in children

Last published:Jun 03, 2025

It’s not always easy to tell if your child is overweight, and many parents may not be aware of the possible health effects.

This information explains what it means for a child to be overweight, why it happens, and why achieving a healthy weight is important.

What does it mean for my child to be overweight?

​When doctors say a child is overweight, they mean their weight is higher than what’s typical for their age and sex. You might also hear the term "obesity" which refers to being very overweight. Being medically overweight or obese means your child has too much fat in their body, which can lead to health problems and may affect their mental wellbeing.

Many parents don’t realise that their child is overweight. This could be for a number of reasons:

• Children grow at different rates, and parents may think this weight gain is just part of normal development, like "puppy fat".

• If a child’s friends or family members have similar body types, parents may think their child’s weight is typical.

• Parents may not notice gradual changes in their child’s appetite or activity levels. This might lead to slow, unnoticed weight gain over time.

How do doctors know if a child is overweight?

Most doctors use the body mass index (BMI for short) to find out whether people are at a healthy weight. Your BMI is a number that's worked out from your height and weight.

For children, doctors compare their BMI to growth charts that show the typical BMI range for children of the same age and sex. This helps determine if your child’s weight is higher than what is considered healthy for their age group.

What causes children to become overweight?

Children become overweight for similar reasons as adults: they consistently eat more calories than their bodies use for energy. The extra calories are stored as fat.

A number of factors can contribute to a child eating more calories than they burn:

• Diet: The type of food your child eats.

• Portion sizes: How much your child eats.

• Physical activity: How active your child is.

Some parents may believe their child is overweight due to genetics. It’s true that genetics can make a child more likely to gain weight. But healthy eating and exercise are still important to help your child maintain a healthy weight.

In rare cases, weight gain can be caused by hormonal issues, medications, or certain genetic conditions (such as Prader-Willi syndrome). If your child is overweight, your child’s doctor will ask you about their lifestyle, and will check for any underlying conditions.

What happens next?

Maintaining a healthy weight is important for your child’s overall health and wellbeing. It can help:

• Reduce the risk of health problems: Overweight children are at greater risk for conditions like asthma, high blood pressure, and high cholesterol. They are also more likely to have problems with the way their body controls blood sugar levels (insulin resistance and diabetes).

• Prevent long-term health problems: Not all overweight children will become overweight adults, but they are more likely to carry excess weight into adulthood. This increases their risk of developing heart disease, diabetes, osteoarthritis, and some cancers.

• Boost self-esteem and mental health: If your child feels upset about their weight, reaching a healthier weight may improve their confidence, wellbeing, and overall happiness.

If you or your doctor are concerned about your child’s weight, it’s important to take steps to help them reach a healthy weight. For more information on how to support your child, including treatment options and strategies, refer to our patient information titled: Obesity and overweight in children: support and treatment.