What Is A Dangerously Low Bmi?

Low body mass index is linked with long life span and better quality of life, according to research reported by Walter Willett in his landmark nutrition manual "Eat, Drink and Be Healthy." Despite what you may have been told, however, you can be too thin--dangerously low BMI has been linked to its own suite of health problems.

BMI Basics

Body weight alone is a poor guide for determining healthy body mass. This is because tall people can weigh more than short people while maintaining a lower percentage of their weight as body fat. The BMI, invented by Belgian statistician Adolphe Quetelet, takes height and weight into account by plugging both into a formula.

Calculating BMI

You calculate BMI by multiplying your weight in pounds by 703, then dividing the total by your height in inches squared. A healthy BMI level is between 18.5 and 24.9. Higher scores indicate overweight and obesity, while lower scores indicate being underweight. According to Janis and Mazzeo of Virginia Commonwealth University, a BMI of 15 or below indicates a dangerously low body weight as compared to height.

Dangers of Low BMI

People with a low BMI are essentially starving to death by not taking in enough calories to maintain a healthy body weight. Some of the health problems associated with this condition include increased risk of osteoporosis, anemia from insufficient iron, a weakened immune system and even organ failure and death. Short-term problems associated with low BMI can include impaired judgment, lethargy and mood swings.

Causes of Low BMI

In the United States, few people are in danger of starving due to lack of access to foods. Rather, a study by Janis and Mazzeo suggests that Americans with abnormally low BMI are often suffering from an eating disorder, most commonly anorexia. Extremely low body weight can also be the result of a handful of medical conditions. Either way, if your body mass index is approaching 15, your best course of action is to see a doctor.