Because the body mass index (BMI) is an indicator of fitness, it is a useful tool for doctors in determining a person’s health. For most people, a normal BMI range is 18.5 to 24.9. People who are underweight have a BMI of 18.5 or lower. When a person has what is considered to be an underweight BMI, clinicians will gather other data and, together with BMI, determine whether there should be concerns regarding malnutrition.
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Body Mass Index
Body mass index (BMI) can determine whether a person has an appropriate weight for his or her height by comparing the proportions between the two measurements. In mathematical terms, body mass equals 703 times the quotient of a person’s body weight divided by the square of his or her height. Invented in the 1800s by a Belgian doctor who studied what was then called “social physics,” BMI was adopted by the National Center for Health Statistics as a measurement tool for health in 1977.
Malnutrition, by definition, is a lack of nourishment caused by illness or an inadequate amount of food intake. Malnourishment is disease-related in nature when the metabolism will not allow the body to take in food appropriately. Worldwide, a nutrient deficiency is most commonly caused by poverty. Malnutrition can also be self-inflicted in cases of eating disorders.
In the western world, eating disorders are a major cause of malnutrition and might be first recognized when the person with the disorder develops a low BMI. While some eating disorders are caused by overeating, the two major disorders relate to severe, self-induced calorie restriction. In cases of anorexia, a person consumes very few or no calories due to a fear of weight gain. In cases of bulimia, a person may eat a great deal but will then force himself to vomit, exercise or use laxatives to make the calories go away.
One in ten people in the U.S. die of an illness caused by eating disorder-related malnutrition.
Malnutrition can have a variety of detrimental effects. From a quality-of-life standpoint, malnutrition can lead to feelings of depression, fatigue, fainting and a general level of fatigue. From a clinical standpoint, extreme cases of malnutrition can lead to reduced organ function, heart problems and death. Children who are undernourished have a higher degree of death from diarrhea and pneumonia. In hospital patients, malnutrition can result in impaired muscle function.
Particularly when it indicates a too-low level of body fat, a low BMI can be dangerous to a woman’s reproductive health. According to the American Council on Exercise, women with less than ten percent body fat can severely compromise their ability to have children and have regular hormone function.
To prevent malnutrition, parents and medical professionals can monitor children’s and adults’ BMIs to ensure that they are in a healthy range. For infants, The World Health Organization recommends that mothers breastfeed their children until the age of two. For adults, the American Dietetic Association recommends moderately active women eat 1,800 to 2,200 calories a day, while men who are moderately active should eat 2,000 to 2,800 calories per day. Even in the case of dieters, women should consume at least 1,200 calories per day, and men should eat at least 1,500 calories per day to avoid problems associated with poor nutrition.