There's quite a bit of research in the health industry studying the effects of obesity on various factors, such as fertility/sperm count, brain function, heart health, cancer risk, and so forth. But there's one major flaw in almost all of these studies… they all use BMI (Body Mass Index) as their measurement to determine obesity.If you've kept up with my writing over the years, you may already know that the use of BMI and other weight-based measurements on individuals and small groups drives me nuts. I'm all for quality research that can link actual obesity to various medical conditions, but using the survey populations typically used (from dozens to a couple thousand participants), BMI is an extremely inaccurate comparison.
It's true that researchers must choose a sample population that they feel represents the larger population studied, and this also leads to assumptions that may not apply to the general population. When using BMI these assumptions become vastly more flawed. Likewise an individual reading these studies is compelled to check his or her own BMI and make life decisions based on this false measurement.
BMI is basically just a height to weight ratio. It is easy to calculate and has been shown to be a good predictor of health in a large population. However, when examining an individual or a small group, it should be relegated to the utter nonsense category. For a large percentage of people striving for a normal BMI is like exercising to get shorter. You just can't do it and if you could, it wouldn't be very healthy.
Actually if you want to lower your BMI very quickly, all you need to do is get taller without gaining any weight. Easy right? No, platform shoes don't count.
Here's the first big problem with BMI: healthy men and women have a different height to weight ratio. Women carry more body fat (for various biological reasons), and men tend to be more muscular and have greater bone density. Overall men tend to be heavier than women, even at the same height. Because BMI is the same calculation for men and women, this means the entire concept of having an ideal weight at each height is flawed to begin with.
Second, and far more importantly, muscle weighs more than fat. A person with a great deal of muscle will be heavier than a person with a similar amount of fat. Having an excess of muscle may have some risks, but they are not at all equivalent to the risks of carrying excess body fat. Also, those who do a lot off load-bearing work or exercise tend to have greater bone density and thicker connective tissue. This also contributes to being heavier at the same height.
After checking the BMI of a lot of people, what I've found is that typically a very healthy and athletic female will have a normal BMI, while a very healthy and athletic male will have a high BMI (overweight). I've seen quite a few women with a normal or slightly overweight BMI that have a body fat percentage that is significantly higher than the healthy range. This is even more dangerous because they don't have the underlying muscle to support it. At the same time, I've seen very athletic women with almost dangerously low body fat levels that are on the high side of a normal BMI.
The main point to take away here is that you need to forget concepts such as "ideal weight" and use body fat percentage as your means of evaluation and progress tracking.
You can calculate your BMI and body fat using the FitDaily calculator tools
