subject: Defining And Measuring Obesity [print this page] Obesity is a disease in which fat has accumulated to the extent that health is impaired. Note that there are three key components to this definition:
1. "Obesity is a disease..." It is only recently that major health authorities such as the World Health Organization and the US Federal Department of Health have acknowledged obesity as a disease. This change is most important as the disease of obesity can now begin to claim attention and an allocation of resources as do all other diseases.
2. "...in which fat has accumulated..." Fat is the key element of obesity. Primarily we are interested in how much fat there is in the body. We are not focused on weight per se. However, as we do not have a simple office method for directly measuring the fat content of the body, we have to use surrogate measures. We could use weight alone, but this would be terribly misleading. The tall person is always likely to be heavier than the shorter person. Therefore, as a minimum, we have to take into account the height as well. Currently, our best way to do this is by using the body mass index of the BMI. We will discuss how we calculate the BMI and look at its strengths and weaknesses below.
3. "...to the extent that health is impaired." We are dealing with a disease that causes disease. The disease of obesity may be expressed in various ways. It may be as type 2 diabetes or as any of the dozens of known diseases that are caused by or made worse by obesity. It may be expressed as a physical or psychological limitation on the quality of your life. For example, you can no longer do the things that are normally expected. You may have severe lowering of self-esteem or self-confidence, leading to isolation, depression or unemployment. Or it may be expressed as a risk to your future health. You may feel fine currently, but you are aware that you are at high risk of disease in the future and that your life expectancy is being reduced by your obesity.
We will look at the disease of obesity in a more detail below but, firstly, let's be clear about how we measure this disease.
The Body Mass Index
The BMI is our best single measure of obesity.
The BMI is a measure that combines the weight and the height according to the following formula: BMI = weight (in pounds) divided by height (in inches) X 705 or
BMI = weight (in kilograms) divided by height (in meters)
