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Why bother to check the math on an exciting and counterintuitive message? “Bicycles less efficient than SUVs!” Or, why you should never blindly trust a column by John Tierney of the NYTimes, and Someone is Wrong on the Internet!

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Two possible (popular) reasons are that we eat too much and exercise too little.

But there’s (at least) ten other possible causes, with some reason to consider them plausible.

  • Sleep debt
  • Endocrine disruptors; chemicals don’t just make us girly-men, they make us fat girly-men.
  • Indoor climate control; sweating and shivering doesn’t so much build character, as reduce your size, so that the character-per-pound increases.
  • Less smoking.
  • This is your blobby body on drugs; all that stuff we take to smooth our moods, makes us eat foods
  • Older mothers (it’s always mom’s fault)
  • Demographics
  • Intrauterine/intergenerational effects
  • Fat = fertile
  • “Non-random mating and floor effects”

All these crazy ideas are explained and semi-justified in the paper.

I found this article a few weeks ago that quantified the risk of physical inactivity (specifically, not biking to work), at a 39% higher mortality rate.

I think that means that if the baseline mortality rate is 750 deaths per 100,000 (that’s about the US mortality rate), then 40% higher would be 300 more deaths, or 1050 per 100,000.
Except, since the norm in the US is non-cycling and mostly inactive, the difference is 214 deaths, from a hypothetically exercising baseline of 536.

Is this a big difference? Probably. We regard working in the fishing and timber industries as being very dangerous (pdf, p. 4), but their additional risks are 200 and 62 deaths per 100,000 per year, respectively.

Seems to me that I ought to be owed a reduction in my life insurance premiums, as long as I keep biking to work.

There’s an internet cycling claim, attributed to Mayer Hillman, that not riding a bike (at all) is ten times more dangerous than riding a bike, because it is so unhealthy to be unfit. I haven’t been able to find the statistics that back up this claim, even when I bought the book from which it allegedly came Cycling: Towards Health and Safety. The closest it comes is the statistic that in a group of commuting cyclists, roadway crashes (of all kinds) accounted for only 1.4% of deaths (whereas heart attacks in this group killed 33%, and the known reduction in heart attack risk with exercise suggests a substantial net reduction in mortality).

However, happily, I just found this:

Even after adjustment for other risk factors, including leisure time physical activity, those who did not cycle to work experienced a 39% higher mortality rate than those who did.

Unless you think a 39% boost in your risk of death is “safe”, a little old unarmored bicycle, no belts, no airbags, no roll cage, is safer than a car, at least for the first 50-100 miles of travel each week.

And there’s more (via UtilityCycling.org):
Conclusions: On average, the estimated health benefits of cycling were substantially larger than the risks relative to car driving for individuals shifting their mode of transport.