Hybrids make you fat!

Sometimes a scientific paper makes me giggle.  The paper by Charles Courtemanche which I’m skimming this morning has a few examples of this.  For example it says that people tend to under report their weight and over report their height; but more the former than the latter.  It also includes this phrase “the food variables are left-censored at zero” – which means to say that the French fries don’t come out of your mouth, they only go in.  This formula where on term is aproximately salads and another term is meatloaf is a hoot.


I don’t know were this guy get’s off announcing that meatloaf isn’t health!  The author took two large data sets, one for prices (that’s gas price in the formula) and one for health behaviors.  The health behavior data he used is collected by the Behavioral Risk Factor Surveillance System of the CDC.  It’s a telephone survey conducted by state health departments.  That survey is full of interesting facts, for example here is a map showing the states and metro-regions where people lack health insurance.


In anycase, he was looking to see if there was some corrolation between gas prices and obesity; and yes cheap gas makes us get fatter.  Given that the next question is “How so?”  The behavior data has lots of info about various things people are doing he can look for patterns there too.  Thus we can can learn the valuable and amusing fact that “A rise in gas prices appears to increase the frequency of hamburger consumption…” and “a small increase in salad consumption”.  From now on when ever I see that the price of gas has gone up I’m going to think “hamburger?”  Generally higher gas prices don’t lead to healthier eating.

People lost weight when gas prices rose for two reasons.  Where they ate changes; they ate more at home.  And they walked more.  I.e. higher gas prices reduced driving; displacing driving to the resturant and increasing walking as a substitute.

His conclusion:

In this paper, I provide evidence of a causal link between gasoline prices and body weight. Using data from the BRFSS, I find nd that a $1 increase in gas prices would, after three years, reduce U.S. obesity by approximately 15%, saving 16,000 lives and $17 billion per year, a  magnitude which offsets 16% of fuel consumers’ additional expenses. I also estimate that 13%  of the U.S.’s rise in obesity over the period 1979-2004 can be attributed to falling gas prices  during that time. Finally, I find that a rise in gas prices increases exercise and decreases the amount people eat out at restaurants, explaining their effect on weight.

This paper is actionable on a personal level.  Lose weight, buy a gas guzzler! But then it is probably twice as effective to buy a car you hate.

The paper is here (pdf), and a nod to the ever facinating Paul for his post about it.

4 thoughts on “Hybrids make you fat!

  1. Joel

    “People lost weight when gas prices rose for two reasons. Where they ate changes; they ate more at home. And they walked more. I.e. higher gas prices reduced driving; displacing driving to the restaurant and increasing walking as a substitute.”

    Walking doesn’t happen when gas prices increase. Higher gas prices reduce driving in the same way that time-of-day parking reduces driving. People are only sensitive to the cost of driving at the margin (the price of gas), mainly and regrettably because they have no idea what the actual cost of driving is. The downside is that if they actually knew how much it cost to drive a car ($0.80-$1/mile), then a rise in the price of gas wouldn’t change their driving at all. They would still drive to a restaurant to eat. Starving children in China, and I paid for it, I’m going to eat it is what makes people fat.

  2. bhyde

    That rising gas prices are correlated with increased walking is one of the results of his analysis. The causality is, as usual, harder to discern. But I’m comfortable with the assertion that rising gas prices will increase the amount of walking.

    You are right that the cost of gas is only a part of the cost of car miles. Your right that people’s behavior would be different if they had a clearer signal about what the car is costing them. There are a number of consumer protection regulations that work by improving the quality of the signal available to the consumer, for example the fair lending laws, and I’d love to see a law passed that required car dashboards to include a more accurate per mile cost.

  3. Joel

    “rising gas prices will increase the amount of walking.”

    Maybe it’s only because I live in suburbia, and have been a runner for 39 years, that I haven’t noticed people substituting walking for driving. If car-substituting walkers are out there, they’re invisible.

    “I’d love to see a law passed that required car dashboards to include a more accurate per mile cost.”

    About 20 years ago there was a move in California, where a lot of drivers had no insurance, to roll the price of insurance into gasoline – everyone would buy their insurance at the pump. It died. But this is still a great idea. It turns a large fixed cost into a variable cost that can be reduced by not using your car. The other large cost is depreciation. A car that isn’t driven isn’t depreciating mechanically, though it may be depreciating in safety and style. There’s a huge incentive to walking, in not driving, if car costs are not permitted to run while the car sits. Sales and property taxes are the other fixed costs and they too could be rolled into the price of gas.

    Cars are status symbols, like yachts, or everyone would be driving the cheapest cars available. Not much rational can be said about status symbols, it’s a pecker-measuring contest, no one wants little cars that are efficient or big cars they’re not going to drive because today they’re going to walk to lunch.

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