If the weight of a person is lower than normal weight range, he or she falls under the category of underweight. Thus, underweight shows that an individual weighs less than is necessary for healthy range. Underweight is often defined by means of BMI - body mass index.

Underweight frequently results from malnutrition. Such diseases as tuberculosis, hyperthyroidism, gastrointestinal disorders, liver affections and cancer may also lead to underweight. Underweight people poorly assimilate nutrients from food. Researchers also found genetic predisposition to underweight.

Underweight people possess modest energy reserves. The immunity of underweight patients is weak making them susceptible to various infections. Underweight people need scrupulous attention because their caloric intake is low and the assimilation of essential amino acids, vitamins and minerals is usually insufficient. Underweight increases the risk of osteoporosis, anaemia and alopecia. Underweight in women may provoke amenorrhea, infertility and pregnancy complications. Underweight may reflect the existence of an underlying, hidden disease. This is why unexpected and difficult-to-explain weight loss requires particular medical alertness. Mortality in underweight is comparable to that in morbid obesity.

Underweight cure presupposes rising of caloric consumption and increasing of food amounts. Healthy diet plays the leading part in underweight condition. Healthy proteins, fats, and carbohydrates are particularly important for competent and skilful weight gain. Butter, cream, olive oil, and nuts are indispensable constituents of healthy diets in this case. Foods with high caloric content such as cheese, dried fruits, and raisins are extremely valuable in underweight. Eating starchy vegetables such as potatoes can also contribute to needed weight gain. Drinking of liquids with high caloric content such as milk and fruit juice can be helpful in underweight. Natural way to increase muscle mass is regular exercise practice.