Question

Please explain what the BMI is. Include in your answer what BMI stands for, how BMI differs for adults and children, and one of the limitations of BMI. Lastly, provide an explanation of the BMI-for-Age percentages for the three categories of what classifies as underweight, at risk for overweight, and overweight.

Answer 1

The letters BMI refer to the a measurement called the body mass index. This value is obtained by using both the mass (weight) and the height of a person. Therefore, it creates broad categories in which people can be classified. These are underweight (under 18.5 kg/m2), normal weight (18.5 to 25), overweight (25 to 30), and obese (over 30).

In order to obtain the BMI, we need to divide the body mass by the square of the body height, and the resulting value would be expressed in units of kg/m2.

The BMI, however, has important limitations. For example, it is not particularly useful if we want to determine the fat levels of a particular person. Taller people, for example, have a BMI that is unusually high when compared to their actual fat levels. Therefore, this measurement is better employed when identifying large populations, as opposed to individuals. Another thing to notice is that BMI applies differently to children. While the measurement is obtained in the same way, these are not compared to standard categories, but to the percentiles of other children of the same sex and age.

Answer 2

The BMI is an effort to measure the quantity of tissue mass, that includes muscle, fat, and bone, in a person. Then classify that person as underweight, normal weight, overweight, or obese which is derived from that value. That classification is the topic of some discussions about where to put the dividing lines between categories on the BMI scale. Regularly acknowledged BMI ranges are underweight which is under 18.5 kg/m2, normal weight which is 18.5 to 25, overweight which is 25 to 30, obese which is over 30. BMI for children is computed similarly as that for adults, but subsequently compared to average values for other children of the same age. One of the limitations of BMI is that it is not comprehensible where the threshold for overweight and obese should be set on the BMI scale. And because of this, the guidelines differ for the past few decades. Furthermore, the BMI is compared with the percentile for children of the same age and sex rather than comparing it against fixed thresholds for underweight and overweight.