Obesity in children: how is it defined and what helps?

If you are worried about your child's weight, growth or eating, talk to your family doctor, paediatrician or school or community nurse. This page is general information and does not replace a personal assessment.

How is obesity defined in children?

Obesity in children is defined by comparing a child's measurements with WHO growth standards for children of the same age and sex. Because children's bodies change as they grow, the adult BMI categories do not apply.

Some countries use their own growth charts and cut-offs expressed as percentiles (centiles). In the United States, for example, the CDC classes a BMI at or above the 85th percentile as overweight and at or above the 95th percentile as obesity for ages 2 to 19.

In the UK, NICE also uses waist-to-height ratio from age 5, with 0.5 or more indicating increased health risk. Our page on BMI and waist size explains these measures.

A single measurement says little on its own. Doctors look at how a child grows over time, and at their health, development and wellbeing.

How common is obesity in children?

Childhood obesity has increased sharply worldwide since 1990. According to the latest WHO estimates:

• 35 million children under 5 have overweight
• 400 million children and adolescents aged 5 to 19 have overweight, including 170 million living with obesity
• the share of 5 to 19 year olds living with obesity has risen from 2 percent in 1990 to 8 percent

Childhood obesity often continues into adulthood. It is linked to early signs of type 2 diabetes and heart disease, but also to stigma, bullying, poorer quality of life and weaker school results.

What causes obesity in children?

Obesity in children develops through a mix of genes, biology and the world children grow up in; it is not the fault of the child or simply of the parents. Factors include:

• Genes and biology: some children inherit a stronger appetite or a tendency to store fat; rare genetic conditions can cause severe obesity from early childhood. See genetics and biology.
• Food environment: easy access to cheap, energy-dense foods and sugary drinks, and heavy marketing aimed at children. See the food environment.
• Activity and screens: fewer safe places to play, less active travel and more time sitting.
• Sleep and stress: short sleep, stress, adverse experiences and mental health problems.
• Early life: factors during pregnancy and infancy, including the parent's health in pregnancy. The WHO recommends breastfeeding, where possible, as part of healthy early nutrition.
• Medicines and health conditions: some medicines and hormone conditions can lead to weight gain.

How is obesity in children treated?

The main treatment for obesity in children is a structured programme that combines healthy eating, physical activity and behaviour change, with parents or caregivers closely involved. The WHO has now published its first global guidelines on obesity in children and adolescents, which:

• strongly recommend structured programmes on diet, physical activity and behaviour change for children and adolescents living with obesity, delivered by trained health workers
• support digital tools only as an extra, with a parent or caregiver supervising
• do not recommend medicines, bariatric surgery or weight-loss devices for children aged 0 to 9
• say that, for ages 10 to 19, approved medicines may be considered only if a supervised lifestyle programme has not worked well enough, and that surgery may be considered under strict conditions for severe obesity
• ask that mental health problems such as anxiety and depression are addressed early and together with obesity

National guidelines vary. In the United States, the American Academy of Pediatrics advises against simply waiting to see whether a child grows out of obesity, and recommends intensive family-based treatment, ideally at least 26 hours of contact over 3 to 12 months.

Good programmes are supportive and do not put children on strict diets. Structured treatment led by trained professionals has not been found to cause eating disorders and may reduce eating disorder symptoms. Availability and costs of programmes, medicines and surgery differ by country.

Treatment aims to improve health, fitness, wellbeing and confidence. For many growing children, the goal is to slow weight gain while they grow taller, rather than to lose weight.

What can families do at home?

Families can help most by making healthy habits normal for everyone in the home, rather than singling out one child. Ideas that work for the whole family:

• Eat regular meals together when you can, with vegetables, fruit and water as easy choices.
• Keep sugary drinks and snacks as occasional foods, without banning or using them as rewards.
• Find activities your child enjoys, and move together, such as walking, cycling or playing outside.
• Agree on screen-time limits and keep screens out of the bedroom at night.
• Keep a regular bedtime so your child gets enough sleep.

How can I talk with my child about weight without stigma?

Talk about health, habits and feeling good rather than weight, size or appearance. Research with more than 2,000 teenagers found that conversations about weight were linked to more dieting and unhealthy weight-control behaviours, while conversations about healthy eating were not.

• Do not blame your child or yourself, and avoid words like diet or fat.
• Praise qualities that have nothing to do with looks, such as kindness, effort or being a good friend.
• If your child brings up their weight, listen calmly and kindly, and ask what they think and feel.
• Agree a family rule: no teasing about anyone's body, and challenge comments about other people's size.
• Model a healthy relationship with food and your own body.
• If your child is bullied about their weight, deal with the bullying with the school; do not change their eating because of it.

Our pages on weight stigma and supporting a loved one give more ideas.

When should I see a doctor?

See a doctor if you are worried about your child's weight or growth, or if weight is rising quickly. Seek help sooner if your child:

• snores loudly, has pauses in breathing at night or is very tired during the day
• has hip, knee or leg pain, or a limp
• has dark, velvety patches of skin in the neck or armpits, or is very thirsty and urinating often
• has frequent headaches or vision problems
• seems low, anxious or withdrawn, or is bullied
• skips meals, eats in secret, makes themselves sick or follows extreme diets
• gained a lot of weight very early in life or has unusual hunger

A doctor can check growth, blood pressure and, if needed, blood tests, and refer you to a specialist programme. Our doctor visit checklist can help you prepare.