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Obesity in Adolescents


Sharon Levy

, MD, MPH, Harvard Medical School

Reviewed/Revised Jul 2022 | Modified Dec 2023
Topic Resources

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 Obesity Obesity (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 Obesity Obesity is a chronic, recurring complex disorder characterized by excess body weight. Obesity is influenced by a combination of factors that includes genetics, hormones, behavior, and the environment... read more 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 Type 2 diabetes Diabetes mellitus is a disorder in which blood sugar (glucose) levels are abnormally high because the body does not produce enough insulin or fails to respond normally to the insulin produced... read more 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.

Overview of Childhood Nutrition and Obesity

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 Hypothyroidism Hypothyroidism is underactivity of the thyroid gland that leads to inadequate production of thyroid hormones and a slowing of vital body functions. Facial expressions become dull, the voice... read more 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 Cushing Syndrome In Cushing syndrome, the level of corticosteroids is excessive, usually due to taking corticosteroid medications or overproduction by the adrenal glands. Cushing syndrome usually results from... read more 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 Metabolic and Bariatric Surgery Metabolic and bariatric (weight-loss) surgery alters the stomach, intestine, or both to produce weight loss in people have obesity or overweight and have metabolic disorders related to obesity... read more ).

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

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