Being underweight can affect a person's health by increasing the risk of conditions such as anemia and osteoporosis. People who are abnormally thin may also be more likely to become ill due to potential immune function disruption.
Being underweight often comes as a result of malnutrition. This can happen from not eating enough, but it can also be caused by other factors that are not allowing the body to absorb and utilize nutrients properly. This is why underweight people can develop deficiencies in key vitamins and minerals. People who are deficient in iron, folate and B12 can become anemic. Anemia manifests itself most commonly through dizziness, exhaustion and headaches.
Nutrient deficiencies can also cause the immune system to become compromised, making underweight people more susceptible to infections and contagious illnesses like the flu. Lack of adequate body fat can cause the body to stop or slow the production of estrogen in women. This can cause issues like infertility and loss of bone density.
People can become underweight for several reasons. Diet and genetics can play a role. People can also become underweight because of medical issues like an overactive thyroid, digestive problems and even undiagnosed diseases. If a person has trouble maintaining a healthy weight despite efforts to increase caloric intake, a doctor should be consulted to check for underlying causes.