Understanding Body Mass Index

Body mass index (BMI), is a mathematical measurement that is used to compare a person’s weight to his or her height. Body mass index is not used to measure a person’s percentage of total fat in the body, but it does help to determine what an appropriate weight should be relative to an individual’s exact height.

It is very easy to calculate the BMI, so physicians and other weight loss professionals regularly use it to help identify if a person is of average weight, underweight, or overweight. This measurement was first developed by a Belgian scientist, Adolphe Quetelet, in 1830, and is still used today by taking a person’s body weight, and then dividing it by the square of his or her height (kg/m2, lbs. x 703/inches2, or lbs. x 4.88/ft2).

The use of body mass index calculations really took hold in the early 1950s, when more and more people began to show signs of a weight problem. This method was a very easy way to determine what level of personal thinness or fatness an individual was at, and allowed physicians to make personalized recommendations to help to correct the issue.

While many find the BMI to be quite useful, some professionals have found defects with the calculation process due to differences in height. People who are taller began to find that their BMI number was quite high when in reality their actual body fat levels did not correspond. This discrepancy was due to the fact that those of a taller stature were not simply scaled up to account for the difference; their BMI was in effect doubled instead of remaining balanced in relation to their specific weight.

Current body mass index levels are as follows: optimal and normal weight allows a BMI of less than 25, however, levels under 18.5 are considered to be underweight, while levels above 25 are considered to be overweight. A BMI level of over 30 is considered to be obese, and a BMI of over 40 is considered to be morbidly obese.

While the BMI is a good starting point to determine your target weight, it should not be taken as gospel. BMI is not able to distinguish between muscle weight and weight from fat. This means that if you are very muscular, and you have the same height as someone who has a good deal of fat, your BMI could actually be higher. The numbers are usually quite off for elderly patients as well. Elderly people tend to have low amounts of lean body mass, which cannot be determined by the index. The BMI has no way to take into account factors such as, age, body fat, gender, general health condition, bone mass, or medical factors.

Even though the body mass index calculation has a few faults, it is still considered among professionals to be a useful tool to help (if even roughly) measure an individual’s level of health. That being said, this index should be used in conjunction with many other evaluation practices before making a conclusive determination as to overall health.