Being underweight can be potentially dangerous especially in case of sickness where the body does not have adequate resources to deal with the infection. Apart from this, some of the common problems of overweight people include poor resistance to illness (they catch infections very easily), persistent weakness/fatigue, hair loss, hormonal imbalances and anemia. Underweight women especially are prone to menstrual irregularities, pregnancy complications, and even infertility.
OsteoporosisOsteoporosis (a condition in which bones become fragile and easily prone to fractures) is a serious complication of being underweight. Intolerance to cold is also one of the common complaints of people who weigh less than normal.
Apart from the above, heart irregularities, memory problems, digestion troubles and depression are frequently associated with being underweight.