Body Mass Index (BMI) is a ratio of weight and height of a person. This is the easiest, cheapest instrument to find out if you are underweight or obese. In some way Body Mass Index can be considered a type of body fat measure. Knowing your body state will help you to foresee and avoid health problems.
Body Mass Index has been elaborated to identify weight problems not only for adults, but for children as well, since children’s obesity is becoming threatening. However, one should mind that Body Mass Index can not be taken as an accurate diagnostic tool.
There are a few moments any physician should take into consideration while assessing if obesity is threatening your health. He should evaluate a person’s diet and physical activity, observe a person’s family history, find out skinfold thickness, and make some more screenings.
Body Mass Index is a reliable tool, since Center for Disease Control (CDC) tends to use it to measure if a person is severely underweight, overweight or obese.
Definitely there are other ways to determine a person’s body state, like computerized tomography, bioelectrical impedance, underwater weighing, but these methods are not always available, require more time and more trained staff, and what is important, they are much more expensive.
Let’s consider the Body Mass Index formula. Measurement units can be different, meters and kilograms, inches and pounds. The formula itself is very simple and it is the same both for adults and children.
Body Mass Index number is weight in kilograms or pounds divided by height in meters squared or inches squared.
While using metric system it’s necessary first to divide height in centimeters by 100 in order to obtain height in meters. For example 155 cm is 1.65 in meters. And then divide weight in kilograms by height in meters squared.
While calculating BMI using inches/pounds system, one should divide weight in pounds by height in inches squared and multiple results by 703, which is a conversion factor.
While interpreting BMI for children, it’s important to take into account that BMI for children and teens under age 20 depends greatly on age and sex.
For adults aged 20 y.o. and more, the weight status categories of BMI for all ages and for women and men are the same.
There exist a specific table showing various parameters, like height, weight ranges, BMI ranges and the corresponding weight categories.
There are several basic weight status categories, Severely Underweight, Underweight, Normal, Overweight, Obese Class I, Obese Class II and Obese Class III.
A person is qualified as
Severely Underweight if his BMI is less than 16.5.
Underweight if his BMI ranges from 16.5 to 18.5
Normal is his BMI is from 18.5 to 25
Overweight if BMI ranges from 25 to 30
Obese Class I if BMI is from 30 to 35
Obese Class II if BMI is 35-40
Obese Class III if BMI equals to 40 and higher.
The BMI number and body fatness ratio is rather strong; however a person’s sex, race and age can influence the correlation. Women having the same BMI as men are likely to have more body fat. Older people having the same BMI as younger adults tend to have more fat. Well trained athletes are a special category as they usually have a high BMI, but unlike ordinary persons, in this case the BMI shows the increased muscularity, and not an increased body fat.
Body Mass Index helps people to control their body state and identify the possible obesity, thus preventing various diseases and consequently lethal outcome. Obese individuals are subject to risky diseases, namely Type 2 diabetes, Coronary heart disease, Sleep apnea and respiratory problems, Hypertension, Stroke, even some cancers and etc.