Being underweight can be very unhealthy leading to many complication for your health. some of these complications include the likes of fatigue all the way to fragile bones.
Lack of vital nourishment basically starts to weaken the body as it does not have what it needs to sustain its own structure, in general the body starts to weaken, break down and shut down.
However, you can be underweight despite getting all the nourishment you need according to the guidelines of what adult men and adult woman should be consuming on a daily basis.
This is usually caused by an overactive thyroid.
The thyroid is a gland that releases thyroid hormones and these primarily control your metabolism.
If the thyroid is overactive then it is releases more of these hormones and this leads to the body burning its resources at a faster rate.
If a person has an overactive thyroid then they should be eating more to compensate for their overactive thyroid.
You can also visit your doctor and if you are diagnosed with an overactive thyroid then there are medications that can regulate the thyroids activity.