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[[File:Body images for obesity.png|thumb|Body images to illustrate [[Obesity]]: Images 1 to 5 show people who are underweight]]

[[File:Body images for obesity.png|thumb|Body images to illustrate [[obesity]]: Images 1 to 5 show people who are underweight.]]

[[File:Underweight 01.jpg|thumb|Image of an uderweight woman]]

[[File:Underweight 01.jpg|thumb|Image of an uderweight woman]]

The term '''underweight''' refers to [[humans]] that have much less [[weight]] than they should. Being underweight is bad for the overall [[health]] of the person affected. It is normal what a person's weights changes over time. Being underweight is often defined using a measure called the [[body mass index]] which calculates a score, based on height and weight. If this score is below 18.5, a person is generally said to be underweight. This is only a general indication, though as the scores must not be calculated for everyone. It does not apply to children and adolescents, for example.

The term '''underweight''' refers to [[humans]] that have much less [[weight]] than they should. Being underweight is bad for the overall [[health]] of the person affected. It is normal that a person's weights changes over time. Being underweight is often defined using a measure called the [[body mass index]] which calculates a score, based on height and weight. If this score is below 18.5, a person is generally said to be underweight. This is only a general indication, though as the scores must not be calculated for everyone. It does not apply to children and adolescents, for example.

Being underweight can have different causes:

Being underweight can have different causes:

*[[Malnutrition]], not eating enough, or eating the wrong kinds of foods. The right kinds may not be available, or they may be too expensive to buy.

*[[Malnutrition]], not eating enough, or eating the wrong kinds of foods. The right kinds may not be available, or they may be too expensive to buy.

* The weight of a person is also determined by [[genetics|genetic]] factors. One of these factors is that some people have a "lighter build" than others.

* The weight of a person is also determined by [[genetics|genetic]] factors. One of these factors is that some people have a "lighter build" than others.

* [[Stress (medicine)|Stress]], [[anxiety]] and [[depression (illness)|depression]] can influence weight

* [[Stress (medicine)|Stress]], [[anxiety]] and [[depression (illness)|depression]] can influence weight.

* There are [[eating disorder]]s that cause people to become underweight. The most common of these are [[anorexia nervosa]] and [[bulimia nervosa]]

* There are [[eating disorder]]s that cause people to become underweight. The most common of these are [[anorexia nervosa]] and [[bulimia nervosa]].

* Sudden unexplained weight loss can point to a [[disease]], such as [[cancer]], [[tuberculosis]], [[hyperthyroidism]], [[Type 1 diabetes]] or [[inflammatory bowel disease]]

* Sudden unexplained weight loss can point to a [[disease]], such as [[cancer]], [[tuberculosis]], [[hyperthyroidism]], [[type 1 diabetes]] or [[inflammatory bowel disease]].

* Sometimes the use of [[illegal drugs|drugs]] leads to weight loss

* Sometimes the use of [[illegal drugs|drugs]] leads to weight loss.

* Organs of the [[digestive tract]] may not be working as expected

* Organs of the [[digestive tract]] may not be working as expected.

* People who train sports too much may be using more energy than they get.

* People who train sports too much may be using more energy than they get.

 

== Problems ==

==Problems==

There are problems that are related to being underweight. Very often being underweight is not the first problem. Rather, it often is the effect of another condition or disease. Unexpected weight loss requires the attention of a doctor. There might be another disease. If that disease is treated, the weight problem also disappears.

There are problems that are related to being underweight. Very often being underweight is not the first problem. Rather, it often is the effect of another condition or disease. Unexpected weight loss requires the attention of a doctor. There might be another disease. If that disease is treated, the weight problem also disappears.

Once they were being underweight, psychically, they may feel sad and worried about their health. Therefore, family and friends should support them to help them get rid of their unhappiness.  

Once they were being underweight, psychically, they may feel sad and worried about their health. Therefore, family and friends should support them to help them get rid of their unhappiness.  

[[Category:Health problems]]

[[Category:Nutrition problems]]