Yesterday on the plane I picked up my Oprah Magazine. They had an article in there titled “The Great Weight Debate” that gave a closer look at BMI (weight in kg/height in meters squared) and health. Anyone who knows me knows I loathe BMI for anything other than what it was originally intended for – examining population-based rates of obesity (epidemiological studies). It was not intended for use with an individual (at least, definitely not without taking into account other measures of health).
My strong feelings about BMI correlate well with the author who wrote this article. BMI alone cannot give a clear picture of health and just because you are an “average” BMI that certainly does not mean you are healthy and those who are over their BMI are not necessarily unhealthy. Let’s take a look at the first scenario. When I was in graduate school I measured body fat levels the entire student athlete population as well as various graduate students, subjects in my thesis study and others. There was one particular grad student who at 5’4″ and 104 pounds would be considered underweight but healthy by BMI standards. Her body fat was a whooping 30% though. She was over-fat and certainly lacked muscular strength (muscle weighs more than fat so her weight would be higher for sure if she had sufficient muscle tissue). Now let’s take a look at scenario #2. As I mentioned, I also took body fat measures for all student athletes. Do you know how many muscular athletes were over their “healthy” BMI? Many.
Now getting back to the Oprah article. This magazine article detailed how a person can have a normal, “healthy” BMI but still have many risk factors for chronic diseases, especially if they do not exercise. On the flip side, they also mentioned a 2007 JAMA (that’s the Journal of the American Medical Association) that mentioned fitness, regardless of weight, is the single strongest predictor of mortality risk. Though I haven’t read this study yet, I have read similar studies published years ago that also indicate just how important physical fitness is.
So, the moral of the story (or blog) is this: If you are underweight or normal weight, look at your disease risk factors and make sure that you are taking good care of the inside of your body. If you are overweight and you are having a tough time with weight loss, find your motivation in physical fitness. If that means that you need to constantly remind yourself about just how important it is to get out there and get active, then do it. Whatever you do, just do something that increases the physical activity in your life.