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Obesity in children

9-minute read

Key facts

  • Childhood obesity is when a child accumulates too much body fat for their age.
  • Your child may be obese if their body mass index or BMI is at the 95th percentile or higher.
  • Helping a child or teenager deal with being obese or overweight means they’re less likely to struggle with weight problems as adults.
  • You can help manage obesity in children by modelling healthy eating habits with them, encouraging lots of physical activity, and limiting screen time.

Obesity is a sensitive topic for children and parents. However, it has become more common for children to be obese or overweight, affecting 1 in 4 Australian children.

Obese or overweight children are more likely to face a wide range of health problems as adults, but parents can help them learn good eating and exercise habits that will carry over into adulthood.

What is obesity in children?

A child or teenager who is obese or overweight will carry more body fat for their age. If your child is obese, they will be in the highest weight range, outside what’s considered healthy for their age. If your child is overweight, their body mass is also outside a healthy range, but not as much as an obese child.

In Australia, around 1 in 6 children aged between 4 and 15 years are considered overweight. One in 14 in this age range are obese.

What are the signs of obesity in children?

The most visible sign of obesity is excess body fat, however it’s not always easy to tell if your child is obese or overweight.

A BMI-for-age score between the 85th and 95th percentile may mean that your child is overweight, while a score that is 95th percentile or greater may be a sign of obesity.

Your child needs to grow, but they are healthiest if they stay within a certain weight range for their age known as a ‘BMI-for-age’. A BMI-for-age score between the 85th and 95th percentile may mean that your child is overweight, while a score at the 95th percentile or greater may indicate they are obese.

You can use NSW Health’s healthy weight calculator to estimate your child’s BMI-for-age. However, most online BMI calculators are designed for people 18 years and over, so it’s a good idea to see your doctor to understand your child’s BMI measurements as they grow.

What causes obesity in children?

For most children, obesity happens because they gradually take in more energy (measured in kilojoules) from eating and drinking than what their body uses to grow, play and exercise. Unused energy is turned into body fat, which over time may increase your child’s body weight beyond what’s healthy for their age.

Behaviours you can change

The following are some causes of childhood obesity and steps that families can take to prevent it:

  • Unhealthy eating habits: Review your family’s portion sizes and intake of high-energy, low-nutrition snack foods and sugary drinks, such as juices, soft drinks and flavoured milk. Consider how often you order takeaway foods and eat out.
  • Too little physical activity: Only 1 in 4 children aged 5 to 12 years get enough physical activity each week. Our overreliance on cars for transport also means both adults and children are less active.
  • Too much screen time: 2 out of 3 children spend more than the recommended maximum of 2 hours a day in front of screens such as computers, televisions, smartphones and tablets.

Other causes

Some causes of obesity and excessive weight gain may be outside your control, such as your child’s metabolic rate, which is how quickly their body uses energy.

Your doctor can also help look out for and address:

How is obesity in children diagnosed?

Body mass index

Your doctor will use a BMI percentile chart to assess whether your child or teenager’s weight is healthy for their age. BMI is calculated as the ratio of weight in kilograms divided by height in metres squared (kg/m2). For children, this is charted across weight information for the whole population as a growth curve.

A healthy BMI for children and teenagers will vary according to their age:

  • a BMI-for-age between the 5th and 85th percentile is considered a healthy weight
  • a BMI-for-age between the 85th and 95th percentile is considered overweight
  • a BMI-for-age at the 95th percentile or greater is considered obese

Because a healthy BMI depends on your child’s age and sex, it’s best to seek professional advice on how to interpret your child’s BMI results.

Waist circumference

Sometimes your doctor may want to measure your child’s waist circumference. This is done using a measuring tape around your child's stomach — at roughly their belly button — and taking their measurement while they breathe out.

How is obesity in children managed?

It’s much easier for children with obesity to achieve a healthy weight when their whole family supports them.

For young children, in particular, focus on maintaining weight rather than weight loss. Help them 'grow into their weight', rather than going on a diet that may cut important nutrients from them while they’re still growing.

Share healthy eating habits

Kids who grow up with healthy eating habits are more likely to make healthy food and drink choices when they’re older.

Here are some suggestions to encourage your child to eat healthily:

  • Eat a wide variety of vegetables, fruit, grains, proteins and reduced-fat dairy foods each day.
  • Cut back on junk foods that contain extra salt, sugar and saturated fat, such as biscuits, cakes, lollies, chips and fast food.
  • Drink water instead of sugary drinks, such as fruit juice and smoothies.
  • Encourage your children to eat only when they are hungry, and to stop when they're full.
  • Explain to your child that some foods are only 'sometimes' foods. Save them for special occasions.
  • Make mealtimes free from screens and eat meals as a family.

See more ideas on healthy eating habits to make with your child.

Get active together

Physical activity is also an important way to achieve and maintain a healthy weight. School-aged children need at least 60 minutes of activity every day.

A great way to encourage your children to be physically active is to do it with them! Here are some ideas:

  • Set an example and be active yourself.
  • Include physical activity in your and your family’s day, such as walking to school and doing household chores together.
  • Make the most of your local bushwalk, bike path, playground or sports field.
  • Get your child to play a team sport.
  • Limit screen-based activities to 2 hours a day for school-aged children, and less than 1 hour a day for preschoolers and toddlers.

How can I talk to my child about obesity?

How you talk to your child about obesity can impact on their willingness to keep a healthy weight.

Keep the focus of your conversation on maintaining a healthy lifestyle and good health. You can consider the following tips:

  • Instead of talking about being 'fat', 'heavy' and 'obese', use phrases like 'above your healthiest weight'.
  • Don’t compare your child to their peers. Discourage them from comparing themselves.
  • Instead of labelling foods or activities as 'good' or 'bad', use words like 'healthy' and 'healthier options'.
  • Don’t make negative comments about your own weight or body shape as your children will pick up on these.
  • Focus on steps towards a healthy lifestyle rather than setting weight loss goals.

When should I take my child to see a doctor?

Healthcare professionals can help you support your child to achieve a healthy weight. If you have questions or if the changes you've made don't seem to be helping, see your doctor and check in with them regularly.

Your doctor can assess your child's weight and provide further advice on lifestyle changes, or refer you to other health professionals such as a paediatrician, dietitian or psychologist.

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What are the complications of obesity in children?

If left unchecked, obesity can cause physical, social and emotional health problems.

Weight-related complications include:

The longer your child carries an unhealthy body weight for their age, the more likely it is that your child will become obese as an adult.

Resources and support

For more information and support, try these resources:

Other languages

Do you prefer other languages than English? Health Translations Victoria has a range of fact sheets on healthy eating and activity for children.

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: May 2020

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