Tuesday, October 21, 2008

Why BMI Doesn't Always Work...

For most of the world's population, BMI is a fairly reliable estimate of body fat. That being said, BMI is not a direct measurement of fatness. It's a mathematical model that closely correlates to body fatness for most people.

But there are outliers that don't fit within the model. I'm one of them.

For my 70 inches of heigh, according to BMI tables if I were to have a BMI of 18.5 to 24.9, which is a normal healthy adult BMI, I'd weigh between 132 and 174 lbs.

At the moment I'm 250 pounds. According to three seperate and relatively high end devices estimating my body fat percentage using Bio-Impedance (BIA) my body fat percentage is measured to be between 25 and 26%.

Assuming a worst case of 26% body fat at my current weight, I am carrying around 65 pounds of fat. That would make my lean body mass 185 pounds.

But, if my lean body mass is 185 pounds, how can my ideal weight top out on the BMI chart at 174? The results of these two seperate measurement systems are incongruent. Either a) all three BIA analyses were grossly incorrect or b) I am some sort of outlyer to the BMI model.

Given the likelyhood of a and b, I have to make the assumption that b is true and that BMI doesn't apply to my body type. This isn't exceedingly surprising. I'm a big guy. With only casual weight training, I can bench press about 300 pounds, which is something many serious body builders strive for. BMI doesn't account for body composition completely.

So then, should BMI be gotten rid of as a measurement of fatness? Probably not, but I think it may be time to reconsider how BMI is used.

For large groups of people it is an excellent tool for measuring fatness, as it is for most of the population accurate, at least according to the CDC. For an individual, trying to measure his or her individual fitness there are better tools readily available.

For an individual, estimating body fat by BIA is likely a superior method. The BIA method is at least very strongly correlated to actual body fat, and in most studys I've read is shown to agree within 5% with more accurate methods like DXA analysis. Additionally, it should be a much more inclusive method, which fits large people as well as smaller people (studies suggest that for some asian people obesity begins at BMI 26 instead of 30 for caucasians) better than BMI can.

Tuesday, October 7, 2008

Pumpkin Pie Ride -- Ottawa, Illinois Oct 5th, 2008

When I started cycling this year, I never imagined I would be finishing the season with a a metric century, in fact I didn't even know what a metric century was. Of course, I'm not very good at doing anything just a little bit... After 3 months of training I completed my first metric century at the 19th Annual Pumpkin Pie Ride. In fact it ended up being just a bit further at 108.8 Km /68 Miles.

The morning started off rainy, and it was only about 43 degrees.

The route took me from Ottawa, IL to Utica, Streator, Marseilles, and finally back to Ottawa. It was a great ride, but those Illinois Valley cyclists sure do like to climb. There were some brutal climbs by Starved Rock and again in Marseilles on what I think is called blueberry hill, but would be more aptly named hillbilly hill. Both climbs were over a half a mile, which is a big hill for a midwesterner. This is the approximate route:

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Coasting in after a very long ride...

The final odometer reading:

So what's next? Well next year I plan on doing a full century (100 miles) and attempting a triathlon, but at this point I think my biggest challenge will be maintaining what I've achieved through a long cold Illinois winter. For the next several months my biking will be done on a trainer, with the occasional outdoor ride if weather permits.

Ride Like An Egyptian 9/27/08

Ride Like An Egyptian was a benefit for the Egyptian theater in Dekalb Illinois. I rode the 50 mile option, which turned into a 55 mile ride due to a road construction related detour. In addition to being a great ride, they have the coolest ride t-shirt ever.