Overweight and Obesity in Children

Overview

Overweight and obesity are common among U.S. children. Rates generally increase as children get older. Obesity is also more common among children who are Hispanic or African American/Black as well as among children living in lower-income households and children who have parents with lower levels of education. 

For more general information on overweight and obesity, and for information about adults, visit the Overweight and Obesity in Adults page.

Overweight and Obesity Definitions in Children

For children age 2 and older, body mass index (BMI) is calculated using weight and height, but instead of using a specific number to define overweight and obesity, the BMI is converted to a percentile. The percentile indicates a child's BMI in relation to the BMl of other children of the same sex and age. Compared to other children of the same age and sex, children age 2 and older are considered to have:

• Healthy Weight if their BMI is at or above the 5th percentile but less than the 85th percentile
• Overweight if their BMI is at or above the 85th percentile but less than the 95th percentile
• Obesity if their BMI is at or above the 95th percentile
• Severe Obesity if their BMI is at or above 120% of the 95th percentile or BMI that is at or above 35 kg/m2 

You can find a BMI calculator for children and teens here. It can be used to calculate BMI percentile for age and sex and show a child’s BMI classification.

For children younger than age 2 years, BMI is not routinely used, and growth is assessed using weight-for-length.

Causes of Overweight and Obesity in Children

Many factors can lead to overweight and obesity in children. These include genes, family history, eating high-calorie foods that are low in nutrients, drinking sugary drinks, not getting enough physical activity, and not getting enough sleep. Other factors may include exposure to certain chemicals in the environment, such as endocrine-disrupting chemicals and air pollution. Some medicines and medical conditions can also increase the risk. Family history is an especially strong risk factor. If one of a child’s biological parents has obesity, the child has a higher risk of having obesity, and the risk is much higher when both parents have obesity.

A child’s weight can also be affected by the mother’s pregnancy. If a mother has obesity, gains too much weight during pregnancy, or has diabetes during pregnancy, the child may be more likely to be born larger than expected and may have a higher chance of developing obesity later in life. Children may also have a higher risk if they are exposed to tobacco smoke before birth. This can happen if the mother smokes during pregnancy or is around secondhand smoke. 

Stressful or harmful childhood experiences may also be linked to obesity. These experiences can include family violence, financial problems, divorce, the death or loss of a parent, abuse, or a parent’s mental illness. These situations can cause long-term stress, which may affect a child’s health and weight. Most cases of overweight and obesity in children happen because of several risk factors working together. In rare cases, severe obesity before age 5 may be caused by a single gene problem. Children with these rare conditions may also have other physical or developmental signs that a health care provider can check.

Health Risks of Overweight and Obesity in Children

Being overweight or having obesity as a child can increase the chances of developing many of the same health problems experienced by adults. These may include breathing problems like sleep apnea and asthma, high blood pressure, abnormal cholesterol, type 2 diabetes, fatty liver disease, and bone and joint problems.  Type 2 diabetes in children is very concerning because in children, it can get worse quickly and cause serious complications. In addition to these health problems, some children who have overweight or obesity may experience weight-related teasing or bullying. This can affect their mental health, causing increased stress, depression and low self-esteem. Children with obesity, especially girls, may go through puberty earlier.  Early puberty can raise the risk of emotional, mental, and behavior problems because the child’s body may be developing faster than their emotional maturity. Finally, children with obesity may be at higher risk for developing heart disease as adults because atherosclerosis, which is an abnormal build-up of substances in the arteries, can begin in childhood and can be worse in children who have obesity, high blood pressure, abnormal cholesterol or diabetes.

Maintaining a Healthy Weight in Children

Preventing overweight and obesity is important for children’s physical and emotional health. Health care providers track children’s growth over time and ask about eating habits, physical activity, sleep, and social factors to help them give advice on how to support a healthy weight and prevent overweight and obesity. Families and caregivers can help by getting the whole family involved in healthy habits. This includes eating nutritious foods, drinking fewer sugary drinks, being active, and getting enough sleep. Specific advice for diet, physical activity and sleep depend on a child’s age. In general, children need meals and snacks that are high in nutrients to help them grow, such as protein foods, vegetables, fruits, healthy fats, and whole grains and drinks low in added sugars. Children also need to be physically active every day. Experts recommend that children ages 3 to 5 years be physically active throughout the day to help them grow and develop. Older children ages 6 to 17 years should get at least 1 hour of moderately vigorous physical activity every day. This should include activities that make the heart beat faster, strengthen muscles, and strengthen bones at least 3 days per week (See: Child Activity: An Overview | Physical Activity Basics). Finally, sleep is also important. Children need more sleep than adults and the amount is higher for younger children. Preschoolers (3-5 years) need 10-13 hours; school aged children (6-12 years) need 9-12 hours; and teens (13-18 years need) need 8-10 hours per 24 hours. See this CDC resource for more information.

Management of Overweight and Obesity in Children

Some children with overweight and obesity may need structured or specialized interventions. Intensive health behavior and lifestyle treatment focuses on the health of the whole child and the whole family, not just the child’s weight. This treatment helps families make changes in nutrition, physical activity, and daily habits. It works best when treatment is delivered in person and provides at least 26 hours of support over several months. The goal is to improve health, support a healthier weight, and build habits that last.

Some children with severe obesity may need more than behavior and lifestyle changes alone. They may need to be checked for medical conditions or genetic causes. For some teens with severe obesity or serious health problems related to weight, health care providers may consider weight-loss medicines or weight-loss surgery, called bariatric and metabolic surgery, and refer them to specialists. It is important to remember that medicines and surgery do not replace healthy habits. Health behavior and lifestyle interventions that include nutrition, physical activity, sleep, and family support remain important parts of treatment.

Find Clinical Trials

Clinical trials uncover better ways to prevent, diagnose, treat, and understand diseases and conditions. To ensure results apply to everyone, volunteers of all ages, sexes, and backgrounds, including both healthy individuals and those with specific medical conditions, are needed. Find NIH clinical trials on overweight and obesity in children.

Research Information

The National Institutes of Health (NIH) is the largest public funder of biomedical research in the world. NIH invests most of its budget in medical research seeking to enhance life and to reduce illness and disability. NIH-funded research has led to breakthroughs and new treatments helping people live longer, healthier lives, and building the research foundation that drives discovery.

NIH is a member of the National Collaborative on Childhood Obesity Research, which brings together leading research funders to accelerate progress on reversing the epidemic of overweight and obesity among U.S. youth. NIH also conducts the Environmental Influences on Child Health Outcomes (ECHO) study, a program that investigates how environmental factors affect child health and development.

Find NIH-funded research projects using NIH RePORTER, a searchable database of current and past research projects supported by NIH and other federal agencies.