Wednesday, November 03, 2010

Le Problème Avoirdupois, deuxième partie

WARNING: even though it's not Halloween, this material may be scary.

In part one, I talked about how a lot of runners, including myself are running to stay trim and still eat all the stuff we like...and I shared my own story of growing blimpy-ness and redemption through running.

But now I'm going to share some data from the National Runners Heath Study. (All of these graphs and information can be found over here.  This study looked at about 8000 runners aged 18 to 49. (Why did they stop so YOUNG? Insulting little zygotes...stuff 'em back in the eggs I say.)

There are some interesting statistics. First, we have this graph:


You can see that the more miles per week you run, the less your weight. Obviously somebody that runs 50 miles per week burns a lot of calories. But, of course it could be that only skinny people can survive running that much or want to run that much. Hard to say. But look at this next graph:
Firstly, before you have a heart attack, I should correct the left axis label, clearly it's labeled 'inches' and should be 'centimeters'. God forbid we have a 7000 runners tromping around with 88 inch waists! Yikes! Somebody tried to "metricate" the graph (in a spasm of guilt no doubt) and failed miserably.

But to the point...you can see for each set of lines (grouped by weekly mileage) that the waistline increases with age. 

Ouch. How bad is it? I quote from the study:

"The average rate of weight gain was the same in men running less than ten miles per week and those exceeding forty, about 3.3 pounds and about 3/4 inches around the waist per decade in a 6' man."

Continuing:

"Statistically, it appears that age-related weight gain and exercise-induced weight loss are independent, additive effects. Middle-aged runners are leaner than more sedentary men not because the processes that promote age-related weight gain are abated, but rather because exercise-induced weight loss offsets weight gain during middle age."

So there you go. If you hold your mileage constant (your calorie burn) you will STILL gain weight as you age. Sooo, that begs the question, "How much more do I need to run to keep this from happening?"

Answer:

"Running distance needs to increase annually, by 1.4 miles per week in order to compensate for the expected increase in waist circumference between ages 20 and 50."

 [UPDATE: These numbers are fishy. 3.3lbs per decade is 10 lbs gain from 20 to 50. This is about 33000 calories of excess over 10 years which is 520 weeks, therefore about 65 excess calories a week. That is about .65 of a mile more running required per week. Where do they get 1.4 miles?. Hmm. Perhaps this study isn't so good after all 8( ]

This means when I'm 75 I'll need to run another 28 miles a week beyond my yearly average now? Clearly exercise becomes more and more important as you get older and your metabolism (or whatever the reason) causes you to get bigger. 

But that much mileage increase  isn't going to fly...or even crawl...I think we'll have to cut back the eating. Darnit!

Of course exercise is good for us in so many other ways than weight loss. In fact, other research shows its much more important to exercise and be overweight than vice versa. But it would have been nice to see running turn off that middle age spreading thing.
Told you it was scary. 

Maybe the data after age 50 shows something better? We can hope!

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What do you think about all this? Please leave me a comment! 8)