Obesity in Adolescents

BySharon Levy, MD, MPH, Harvard Medical School
Reviewed/Revised Jul 2022 | Modified Dec 2023

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, and some children may be given medication for weight loss or weight-loss surgery.

Obesity is defined by the body mass index (BMI). Adolescents whose BMI is in the top 5% for their age and gender are considered to have obesity. 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, adolescents with obesity are more likely than their peers to have high blood pressure and type 2 diabetes. Although fewer than one third of adults with obesity were obese as adolescents, most adolescents with obesity become adults with obesity.

Despite many treatment approaches, obesity is one of the most difficult problems to treat, and long-term success rates remain low.

(See also Introduction to Problems in Adolescents.)

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 adolescent with obesity 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, and obesity may be more common among members of the same family.

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

Treatment of Obesity in Adolescents

  • Healthy eating and exercise habits

  • For adolescents 12 years old and older with a BMI at or over the 95th percentile, weight-loss medications

  • For adolescents 13 years old and older with a BMI significantly over the 95th percentile, evaluation for weight-loss surgery

All children and adolescents with obesity are given intensive strategies to help them develop healthy eating and exercise habits and make changes to their health behavior.

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

Adolescents 12 years old and older with obesity (BMI at or over the 95th percentile for age and gender) may be given medications for weight loss.

Adolescents 13 years old and older with severe obesity (BMI significantly above the 95th percentile for age and gender) may be referred to a surgeon who specializes in this area for a full evaluation for weight-loss surgery (bariatric surgery).

Counseling to help adolescents cope with social problems, including poor self-esteem, may be helpful.

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