Well it depends on who is asking? If it is your insurance company, they are probably going off of BMI alone and a recent study from UCLA finds that 54 million Americans may have been mislabeled as obese or overweight, according to the LA Times.
Despite conventional wisdom, research has shown that people with high BMI's can actually be in great shape and those with "healthy" BMI's can be unhealthy. A. Janet Tomiyama, the study's lead author, reports that cholesterol, triglyceride levels, bp, and blood sugar were analyzed along with BMI. Unfortunately, new rules proposed by the Equal Employment Opportunity Commission, could see millions of Americans unnecessarily penalized financially.
A more accurate measure may be a combination of BMI & Body Fat percentage along with analysis of key health markers. The testing is more involved, but it is better indicator of a person's fitness level. Two people may look similar, and have the same BMI, but they could actually have very different body fat amounts.
The big commonly known fault with BMI, and the reason behind its generality, is that the number does not take muscle mass into account. This makes BMI misleading in two ways:
- Firstly, a person who is underweight or normal on the BMI scale may still have a high percentage of body fat, meaning a lower level of fitness.
- On the flip side, a person with a large amount of muscle mass, for example a football player or bodybuilder, could be told by the BMI ranking that he or she is morbidly overweight, when the individual in fact has a low percent body fat and high fitness level.
The bottom line is that BMI is a general overview and should only be an introductory assessment of a person's body composition. It's perhaps useful when more involved testing is not available. For more truth behind the matter, look at percent body fat.