What Are the Health Risks of Being Underweight?

The National Institute of Health uses body mass index (BMI) as the standard measure of body fat, with a normal range of between 18.5 and 24.9. This means that a person with a BMI below 18.5 is considered clinically underweight. With the growing concern over the dangers of obesity, it's hard to imagine that being thin could also pose health risks. But people who are underweight may be vulnerable to equally serious medical issues.

Weakened Immune System

• Underweight individuals often have fragile immune systems, putting them at risk of contracting infections and viruses. They may also feel weak and experience chronic fatigue.

Osteoporosis

• Failing to consume food with the proper nutrients can cause lasting damage to the bones. Osteoporosis, which is linked to insufficient amounts of calcium in the diet, is a condition that causes the bones to become weak and brittle. Underweight people are at risk for developing osteoporosis, according to the National Osteoporosis Foundation.

Reproductive Issues

• Women who are very thin may stop ovulating, experience irregular periods or face fertility issues. Underweight women who are pregnant may go into premature labor or deliver babies with low birth weights, which can lead to developmental problems.

Anemia

• Underweight individuals are also at risk of developing anemia. People with anemia have a low number of red blood cells, usually as a result of an iron-deficient diet. This poses health risks because red blood cells contain hemoglobin, which is a protein that helps carry oxygen throughout the body.

Hair Loss

• When people are underweight, they may experience hair thinning or loss as a result of malnutrition. Additionally, people who are drastically thin may grow a fine layer of hair called lanugo on their arms, legs or stomach.