Have you ever gone to the doctor and seen that body mass index (BMI) chart? Supposedly, this measure tells whether you are underweight, normal, overweight or obese. While this information is good to know and having an equation give us the standard is helpful in general, it doesn’t tell the whole story.
This guy to the right is my husband (he’s so kind to allow me to put his photo online – and a bike short photo to boot!). Oh, and that’s our pup. He has very little body fat and measures in at 6’2″ and 190 pounds. He will be our case study today to demonstrate how absurd BMI really is, but first, a little about how BMI works.
Calculating BMI (body mass index)
Calculating BMI is done by a simple calculation of weight times height in inches times something else – it doesn’t matter that you know these details (clearly I don’t) since simple calculators exist online that do this work for you. Here is one good example.
Simply put in your height and weight, click calculate and voila, you know your BMI. This handsome guy in spandex clocks in at 24.4. In general, the higher your BMI, the more risk you have for certain ailments like heart disease.
Once you know your number, you need to know what that number means. Here is the breakdown:
18.5 and below = Underweight
18.5 – 24. 9 = Normal
25 – 29.9 = Overweight
30 and above = Obese
Sounds simple enough, right? Well, that’s go back to our lovely model. At a BMI of 24.4, he is on the border of overweight. Still technically normal, but not by much. Now scroll back up and look at the photo again. Do you think he looks nearly overweight?
Why BMI Doesn’t Matter
BMI, while somewhat helpful, is full of limitations. First, being underweight can be just as unhealthy as being overweight, just with a bit different implications. Secondly, it doesn’t take into account muscle versus fat. Muscle weighs more than fat and having an athletic or muscular build often comes with a higher scale number than being scrawny, but muscle and fat are very different in terms of assessing a healthy body and healthy weight.
On the flip side, people who have lost muscle and bone mass (particularly elderly or ill people), BMI might say normal but really the person has an unhealthy amount of body fat.
Simply put, BMI isn’t accurate in assessing the true health risks you have. It just doesn’t take enough information into account, like age, genetics, race, activity, body shape, fitness level, lean muscle mass, dietary habits, lifestyle preferences (smoking, etc.) and so on. All people are much more complex than BMI accounts for.
However, it is free, simple, basic and may shed light on whether you could be at an increased risk for weight-related disease. Should you learn your BMI, yes. But should you let it get you down, no. If you’re really concerned about your physical state and whether you are at increased risk for disease, get a comprehensive analysis done. One place to start is at your local fitness center. Many offer complete tests, some with really complex machinery and blood tests. Start there and ask if anyone locally offers this kind of testing.
And more so than a number or a generalized test, trust yourself on this one. Do you think you could lose a couple pounds? Than you probably could. Do you think you’re totally healthy? Than you probably are. Do you think you should put on some weight (i.e. muscle)? Than hit the gym. If you’re TRULY honest with yourself, you know where you’re at.
Calculate your BMI and tell me in the comments, were you surprised at what it said?
(For fair disclosure, my BMI is 22.1, which is in the center of normal, but I could stand to convert some fat to lean muscle mass for sure.)