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Obesity in Adolescents


Sharon Levy

, MD, MPH, Harvard Medical School

Last full review/revision Sep 2020| Content last modified Sep 2020
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Obesity is defined as a body mass index (BMI) equal to or greater than the 95th percentile for age and gender.

  • Although genetics and some disorders cause obesity, most adolescent obesity results from a lack of physical activity and consuming more calories than needed for activity level.

  • The diagnosis is based on a BMI at or over the 95th percentile for age and gender.

  • Eating a nutritious diet and increasing exercise help treat obesity.

Obesity is defined by the body mass index (BMI). BMI is weight (in kilograms) divided by height (in meters) squared. Adolescents whose BMI is in the top 5% for their age and gender are considered obese. Being in the top 5% means their BMI is higher than 95% of their peers (at or over the 95th percentile).

Obesity is twice as common among adolescents as it was 30 years ago. Although most of the complications of obesity occur in adulthood, obese adolescents are more likely than their peers to have high blood pressure and type 2 diabetes. Although fewer than one third of obese adults were obese as adolescents, most obese adolescents remain obese in adulthood.

Causes of Obesity in Adolescents

The factors that influence obesity among adolescents are the same as those among adults. Hormonal disorders, such as an underactive thyroid gland (hypothyroidism) or overactive adrenal glands, may result in obesity but are rarely the cause. Adolescents with weight gain caused by hormonal disorders are usually short and most often have other signs of the underlying disorder. Any obese adolescent who is short and has high blood pressure should be tested for the hormonal disorder Cushing syndrome. Genetics play a role, which means that some people are at greater risk of obesity than others.

Because of society’s stigma against obesity, many obese adolescents have a poor self-image and may become socially isolated.

Treatment of Obesity in Adolescents

  • Healthy eating and exercise habits

The treatment of adolescent obesity is focused on developing healthy eating and exercise habits rather than on losing a specific amount of weight. Reducing calorie intake and burning calories are two ways to meet these goals.

Calorie intake is reduced by

  • Establishing a well-balanced diet of ordinary foods

  • Making permanent changes in eating habits

Calorie burning is increased by

  • Increasing physical activity

Summer camps for obese adolescents may help them lose weight, but if they do not continue the weight loss effort once camp ends, the weight usually is regained. Counseling to help adolescents cope with social problems, including poor self-esteem, may be helpful.

Drugs that help reduce weight are generally not used during adolescence because of concerns about safety. One exception is for obese adolescents with a strong family history of type 2 diabetes. They are at risk of developing diabetes. The drug metformin, which is used to treat diabetes, may help them lose weight and also lower their risk of becoming diabetic.

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