The Body Mass Index (BMI) is the ratio of weight to height and is used to classify people as being “underweight,” “normal,” or “obese” (BMI Classification, 2007). Using the international classifications, a BMI of 32.2 would be considered as Obese Gr. 1. The case being answered is why is a person who eats normally at 4-5 fairly healthy meals every day, satisfies the recommended allowances classified as obese?
Many factors must be considered when answering this case. Most important among these is whether the measurement of the BMI is done under normal conditions, that is, if the body type, health status, body composition and metabolic function of the patient are considered. Truly, there are some instances when the BMI classification is not applicable.
It must be noted that the Body Mass Index is a standard for determining the risk of normal people. It cannot be used for people who have high muscle mass. Muscle is considered as heavier compared to fat and a more muscular person would naturally be higher in body weight compared to his or her “more normal” counterpart. Two persons, for example may have a 32.2 BMI but may have different body compositions: one may appear “fat” because of greater body fat composition and the other may appear really lean and healthy because his or her body composition is mainly of muscles.
The results of the Body Mass Index can also be influenced by the water composition in the body. If the person is retaining water, for example, he or she should not be classified using the BMI standards because the weight is affected by the unnecessary water that is retained inside the body. If water is retained and the person is measured, the BMI would naturally result to a higher value which would not represent the person’s true health status. Edema or water retention can sometimes happen to people with kidney failure, and to women who are pregnant.
The BMI classification should also not be used to pregnant women because in measuring the BMI, the weight of the unborn child is not considered which could also erroneously increase the true value of the index. The result would then, not become representative of the true health status of the individual.
If however, the patient is not “muscular”, the relatively high BMI of the person, despite his or her normal intake can be attributable to the person’s rate of metabolism. There is a possibility of the person having low metabolism as a result of previous abnormalities in dietary practices and intake or possibly a thyroid disorder. Hypothyroidism can decrease the rate of metabolism of a person by as much as 30%. At such rate, the person, no matter how healthy his or her eating habits are, is at risk to gaining more weight, having higher BMI and thus, being at risk to the diseases associated with higher BMI.
These factors must be considered first in assessing whether there is something significant in the BMI of the patient under study. The 32.2 BMI of the person may not be signifying a risk in health but a mere indication of erroneous use of the classification without considering the body composition, water retention, or pregnancy. But if these factors are considered, the person must really be at risk for high fat deposition as a result of low rate of metabolism. The person should then consider doing more physical activity or consulting a doctor on how to normalize the thyroid function.
BMI Classification. (2007). World Health Organization. Retrieved 26 Feb 2007 from http://www.who.int/bmi/index.jsp?introPage=intro_3.html,
Whitney, Cataldo and Rolfes. (2002). Understanding Normal and Clinical Nutrition. 6th ed. Stamford, CT: Wadsworth Thomson Learning.