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 Obesity 
(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 Obesity Obesity is excess body weight. Obesity is influenced by a combination of factors, which usually results in consuming more calories than the body needs. These factors may include physical inactivity... read more 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 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 
. Although fewer than one third of obese adults were obese as adolescents, most obese adolescents remain obese in adulthood.
(See also Introduction to Problems in Adolescents Introduction to Problems in Adolescents For most children, adolescence is a period of good physical health. The most common problems during adolescence relate to Growth and development School Childhood illnesses that continue into... read more .)
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 
) 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 Cushing Syndrome In Cushing syndrome, the level of corticosteroids is excessive, usually due to taking corticosteroid drugs or overproduction by the adrenal glands. Cushing syndrome usually results from taking... read more 
. 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.
