What Are the Dangers of Being Underweight?

With the growing obesity epidemic in the United States, there's news daily about the health dangers of being obese. But what about being underweight? Weighing too little can also have severe health consequences. Though some people are naturally smaller than others, being too thin can wreak havoc on many different body systems.

Definition

• Medically speaking, someone is considered to be underweight if their body mass index (BMI) is under 18.5. Body mass index is a measure of weight relative to height and is used to determine whether someone is in a healthy weight range. The problem of being underweight is not discussed as often as obesity because only 1.8 percent of American adults are underweight.

Causes

• People are underweight for different reasons. Some people just stay thin naturally and don't gain weight no matter what they eat. This may be true if thinness runs in the family. Being underweight can also be a result of living situations. Impoverished people are sometimes too thin because they simply aren't able to get enough nutrients from food. Other people are underweight by choice. An extremely strict diet, excessive exercising and eating disorders like anorexia can also contribute to being underweight.

Reproductive Issues

• A healthy weight can help make a healthy reproductive system. Being underweight can cause problems in the areas of menstruation, ovulation and pregnancy. Women who are too thin may start to miss periods or have them irregularly. They also may experience difficulties in becoming pregnant or maintaining a healthy pregnancy.

Immunity

• Being underweight can also weaken your immune system. People who are underweight cannot fight off viruses and infections as easily as people who are at a healthy weight. The weakened state of the immune system leaves an underweight person at risk to contract diseases and to heal more slowly. They also may have lower levels of energy, making them tired and cold often.

Bone Health

• Being underweight can also have a devastating effect on bone health. Crash dieting, anorexia and long periods of being underweight can deplete bones of essential nutrients and calcium. This can cause diseases like osteoporosis. Osteoporosis is a condition that causes bones to become weak and brittle, breaking easily. Bearing weight on the bones helps to strengthen them, so it is not surprising that being underweight may make them frail.

Hair Loss and Growth

• Being underweight can also cause hair loss. If a person is severely underweight, their body basically goes into a state of stress. They may not be getting enough nutrition for healthy hair growth. This can cause hair to start to fall out. Many people with anorexia may get a growth of downy hair all over their body because they lose some of their ability to regulate body temperature.