Brooks on evolution and obesity

Rob Brooks has posted an article (also published in The Conversation) outlining his argument that the relatively cheap price of carbohydrates compared to the price of protein is driving the obesity crisis. Drawing on material from his book Sex, Genes and Rock ‘n’ Roll: How Evolution Has Shaped the Modern World, Rob argues that as our recent evolutionary history involved a diet of lean meat and high fibre plant foods, modern humans are poorly evolved for the cheap simple carbohydrates that dominate many modern diets.

I have considered Rob’s arguments and policy suggestions in an earlier post, but there is one element in Rob’s post that I would like to discuss. At the end of his post, he writes:

New York’s mayor, Michael Bloomberg, infuriated civil liberties groups and the sugar and soda lobbies last October when he asked the US Department of Agriculture to allow New York City to ban the 1.7 million citizens who receive food stamps from using them to buy soda.

Those Americans poor enough to receive food stamps are precisely the people most at risk of obesity: people with enough access to food that they do not starve, but not enough money to eat a healthy diet with plenty of protein.

So did Mayor Bloomberg have the right idea? Should we tell people what they can and can’t eat or drink? Libertarians love to tell us that we have a choice, and that nobody is forced to overeat.

Despite describing myself as having libertarian leanings, I don’t think this is a bad idea. Bloomberg is not telling people what to eat or drink. If the food stamp users wish to consume sugary products using their own resources, they are free to do so. Similarly, they cannot buy cigarettes with food stamps, but they are still free to smoke.

I usually extend this idea across any provision of government services. While I would often prefer that they were not provided to begin with, placing conditions on access is not restricting liberty as long as the option to take action as a private citizen remains. If the conditions become tight enough, the government service disappears altogether (not that I am arguing that is what should be done with food stamps).

So, controlling use of food stamps among a group most vulnerable to obesity might be a good place to start. However, what I would like to see are some random trials of controlling food stamp expenditure. While state by state comparisons will produce some useful evidence, a random trial would give some evidential meat to the argument that restricting access to sugar will work in practice.

2 comments

  1. While I wouldn’t argue against a random trial (noting the impossibility in this case of a double-blind one), I suspect that in the short term it is unlikely to show much effect; it may have to continue for rather a long time before we can conclude whether or not the policy is effective.

    Heavy consumers of soda may be dependent on the product for their necessary daily intake of fluids – heavily habituated, even perhaps to the point of psychological addiction. Bloomberg theorises that banning use of food stamps may change demand for soda but what might the demand elasticity be?

    In the case of smoking (http://www.tobaccoinaustralia.org.au/chapter-17-economics/17-5-economic-analysis-economic-evaluation-and-eco):

    “There is strong evidence linking increases in price to decreases in demand for tobacco products, the consensus being that price elasticity is inversely related to age. Increases in tobacco tax, therefore, are considered to be one of the most effective tools for decreasing smoking especially among children.”

    The same may be true with sugar-containing soft drinks (although in the US the sweetener of choice is usually high fructose corn syrup). In the case of tobacco, smokers typically start in their teens when they are old enough to make an economic choice between the cachet (such as it is) of being a smoker and the cost. But soda consumption in children of heavy user families begins in early childhood before the economic consequences are apparent to a child. Therefore improvements in obesity rate, if indeed reduction or elimination of soda from diets results in them, depend on people reducing or discarding a habit rather than not starting it.

    If this surmise is correct, it could take 20 years to conclude whether or not the measure was effective. Possibly a more effective strategy is a series of sharp excise tax increases which, as in the case of tobacco, provide an impetus to consumers of the product to reconsider.

    1. Thanks for your comment Mike. I tend to be more optimistic as to the short term effect of a trial of restricting soda purchases through food stamps, particularly with a large sample – but that of course is something that can only be established with a trial. I agree that excise taxes could be effective in reducing sugar consumption (people respond to incentives), but as I posted about before, I have other concerns about their use.

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