Day 18 - BMI and the Apocalypse

Yes, Randi, I reused the Day 8 sign.

If the world as we know it ends today, I'd like to clear up a few things about body mass index (BMI) we all should know before we shuffle this mortal coil (or run around smacking zombies with improvised weapons, or however this is supposed to work).

Body mass index is a calculation that takes into account your weight and height and gives you an estimate of your fatness. In other words, it purports to tell you whether you are at a healthy weight for your height. If you're curious about your own BMI, you can use this online tool to calculate it

I often hear BMI treated as the definitive word on healthy weight. People will tell you, for instance, that you are "safe" if your BMI is below a certain number (usually 25), implying that a BMI above that number is "unsafe".

In actuality, BMI is a screening tool that identifies people in weight categories considered high risk for cardiovascular disease, obstructive sleep apnea, Type II diabetes, and other health conditions that are often linked to high weight. Screening tools are helpful in medicine - they facilitate early detection of cancers, modification of cardiovascular risk factors, and early treatment of a number of conditions that are easier to manage when caught early. But screening tools are sensitive by necessity - this means that they pick up as many cases as possible by using rules and categories that aren't too stringent. They can't be too complicated, involved, or expensive. They are quick and dirty ways of splitting people into higher and lower risk categories, and they are general.

It is possible to be perfectly healthy with a high BMI and perfectly unhealthy with a normal BMI. 

As anyone who has ever tried to lose weight through physical activity knows, muscle weighs more than fat by volume. This means that very muscular athletic people are not served well by BMI. An athlete's BMI may indicate that they are overweight, or even obese - and thus at high risk for cardiovascular disease - when they are fit, trim, and in excellent cardiovascular health. On the other hand, someone who consistently eats junk, is physically inactive, or smokes cigarettes has an elevated risk of cardiovascular disease even with a normal BMI. BMI doesn't take into account body frame or age, and special tables or cut-offs may be appropriate for different ethnicities.


For those interested, my BMI is 27.5, meaning I fall into the overweight category. I did a treadmill test a couple of weeks ago (for an arrhythmia, not coronary artery disease) and was credited with one of the fastest cardiac recoveries from running that the technician had ever seen. In other words, my cardiovascular health is excellent, and this is supported by a recent panel of bloodwork (and, uh, the fact that I ran a half marathon a couple months ago...).

I'm not saying that BMI is not a good screening tool; it definitely has its uses. But if you decide to calculate your own, bear in mind its limitations. Don't get too stuck on the number.

 As for my workout, I did not want to do a single thing today. I wanted to stay home and bake and feed catnip to the cats.

Butter and chocolate make the world go round.

Cats on catnip = best entertainment value.

I offered myself options: Did I want to go for a run? No thanks. Yoga for Athletes? Nope. Swimming at the ARC? Hells no. I may have been in a bad mood following removing a truly gag-inducing wad of hair from the bathroom sink drain, I'll admit, but nothing appealed. It probably didn't help that the streets became a disgusting mess of freezing rain toward the evening.

Freezing rain is not pretty.

What finally got me to the gym was the realisation that I needed baking supplies. The grocery store is right across from the gym, so I could hardly ignore it. So yeah, I did 35 minutes on the elliptical and ran a few kilometres on the treadmill. It did not magically improve my mood, but having this song come up on shuffle did.

Dear feet, I don't want to and you don't want to, but let's do this shit so we can go home.