It is a fact that anything that is either in excess or deficient cause disease if left uncontrolled. Thinness or emaciation is the condition when there is weight loss, either gradually or suddenly. Active illnesses, as in any fever like typhoid, measles make one thinner. There are three types of people who are extremely thin. Some children are born thin inheriting their parent's physical built.
Some children eat all the time but they never sit still for a minute.
Even at home they are never seen idle. In such cases whatever the child consumes, gets converted into energy because of his over activeness. This type of thinness, there fore, need not be cause for worry at all. No amount of tonics and special food can make them gain weight. The resultant low resistance of the body invites diseases leading to emaciation.