From ArticleWorld

A person who is considered below a healthy body weight is said to be underweight.


Body mass index

The term underweight usually is discussed in reference to one’s body mass index. In most cases, individuals with a BMI less than 18.5 are said to be underweight. In some cases, people define underweight as anyone with a BMI less than 20.

The BMI is calculated by weight over height squared. It is a statistical estimate and health of individuals should be assessed on a case-by-case basis.


People who are underweight usually have poor stamina as well as an extremely weak immune system. This leaves them open to infection.

Individuals who are underweight are also at an increased risk of heart disease, blood vessel disease and osteoporosis. Women face an additional health problem: Underweight women may suffer from amenorrhoea, the clinical term for absence of periods and may later experience complications during their pregnancies.


People who are underweight may suffer from this condition due to a poor diet or starvation (also known as malnutrition), psychological problems (anorexia nervosa or body dysmorphic disorder, for example), weight loss due to chronic illnesses (like tuberculosis or cancer), hyperthyroidism and drug use.


People who are underweight must increase their calorie intakes so that they consume more calories than they use as energy. Weight training is also suggested to increase the muscle mass of underweight individuals.

Other issues

People who are underweight are contrasted to people who are overweight; overweight people are prone to obesity or morbid obesity. Typically overweight is identified, as people with a BMI greater than 25, obese people are those with a BMI over 30.