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Unwanted Weight Loss in Teenagers

By Rose Welton ; Updated July 18, 2017

Although some weight loss is intentional, it is possible to experience weight loss that is unwanted and appears to be unexplainable. If this is happening to your teenager, it can be frightening to consider all of the possible causes. Talk to your teenager’s doctor so you can help diagnose and treat the problem effectively.


Unwanted weight loss in teenagers can be the result of cancer, depression, gastrointestinal diseases, hyperthyroidism or malnutrition. Most of these conditions have other symptoms, in addition to weight loss. For example, depression can be accompanied by trouble sleeping, difficulty concentrating, agitation and fatigue. A gastrointestinal disease can cause a loss of appetite and chronic diarrhea.

Other Causes

Drug or tobacco use can cause your teenager to lose weight. If he has painful mouth sores or braces, he may eat less, resulting in potentially unwanted weight loss. An infection, such as tuberculosis, can also be the cause, as well as the use of medications that can cause weight changes.

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To determine the cause of your teenager’s unwanted weight loss, her doctor will need to ask questions. The doctor may ask when the weight loss began, if it was a sudden or gradual change, and if your teenager is experiencing stress or any other changes. He will also ask about her eating and exercising habits. A blood test or x-ray may be able to determine the cause. If no medical cause is found, your teenager’s doctor may consider the possibility of depression.


To treat unwanted weight loss, your teenager’s underlying cause must be treated first. If his weight loss is due to medications, stopping the use of the medication may help. Cancer, gastrointestinal diseases and infections all require medical treatment. Hyperthyroidism can be treated with hormonal therapy. Depression is treated with therapy and antidepressants. Take your teenager to a dentist if he is losing weight due to oral or dental problems.


Because there are so many causes of unwanted weight loss, some of which are more serious than others, it is important to talk to your teenager’s doctor to rule out serious conditions. MayoClinic.com states that the weight loss may be the result of something serious if your teenager loses 10 lbs. or more than 5 percent of her body weight in a six- to 12-month period.

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