Underweight - a term with many question marks

Underweight is a medical phenomenon, to which much research is needed. More or less seems clear that the people affected stimulus threshold is lowered and the vegetative (unconscious) nervous system particularly sensitive to weather influences react - tiredness, fatigue or headaches are the result. To distinguish them is the weather sensitivity - including those suffering from people with diseases such as rheumatism, cardiovascular problems, asthma or fractures. They reinforce the complaints because of the weather. 
In studies on the topic often lack the separation of these two terms and it is often unclear exactly what criteria must be met in order to weather can be spoken. Nevertheless, there are many studies that a connection between the weather and the onset of disease or headaches suggest.