Obesity means weighing more than what is healthy for a given height. Obesity is a serious, chronic disease. It can lead to other health problems, including diabetes, heart disease, and some cancers.

Obesity is becoming much more common in childhood. Most often, it begins between the ages of 5 and 6 years and in adolescence.

Child health experts recommend that children be screened for obesity at age 2 years. If needed, they should be referred to weight management programs.

Your child's mass index (BMI) is calculated using height and weight. A health care provider can use BMI to estimate how much body fat your child has.

Measuring body fat and diagnosing obesity in children is different than measuring these in adults. In children:

• The amount of body fat changes with age. Because of this, a BMI is harder to interpret during puberty and periods of rapid growth.
• Girls and boys have different amounts of body fat.

A BMI level that says a child has obesity at one age may be normal for a child at a different age. To determine if a child is overweight or has obesity, experts compare BMI levels of children at the same age to each other. They use a special chart to decide whether a child's weight is healthy or not.

• If a child's BMI is higher than 85% (85 out of 100) of other children their age and sex, they are considered at risk of being overweight.
• If a child's BMI is higher than 95% (95 out of 100) of other children their age and sex, they are considered to be overweight or have obesity.

Gahagan S. Overweight and obesity. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 60.

O'Connor EA, Evans CV, Burda BU, Walsh ES, Eder M, Lozano P. Screening for obesity and intervention for weight management in children and adolescents: evidence report and systematic review for the US Preventive Services Task Force. JAMA. 2017;317(23):2427-2444. PMID: 28632873 pubmed.ncbi.nlm.nih.gov/28632873/.