To Megan McArdle's "thinking thin" post about the causes of obesity, the relevant question for policy-makers is not whether there is a mono-causal explanation for obesity, it is whether policy-makers can and should do something about it. If everyone responded to the pressures of (a) a corn diet (b) TV advertising (c) the ubiquity of fat and sugary foods (d) the information disseminated by the government and the diet industry (e) technological enabling of a sedentary lifestyle in the same way, it is relatively easy to answer the question. If you tend to blame individuals for their choices, then your answer will be no. But the crucial fact is that obesity does not treat everyone equally. It discriminates according to status, class and geography. And its negative externalities are absorbed by these vulnerable populations. And in children, being overweight is increasingly become the default. Unless someone intervenes, if you go with the flow, if you live in a vulnerable population, you're going to be quite vulnerable to an obesogenic lifestyle. This debate isn't about government dictating lifestyle choices to adults. It's about whether changing policy can reduce obesity among children.
It's easy to say that we're obese because we like to consume fatty, sugary, salty foods, which just happen (actually, because of subsidies and policy, at least partly) to be cheaper. Since we enjoy the food, why should the government get in the business of telling people that enjoying food and valuing this enjoyment over health is a bad thing? Especially if the science is murky?
The idea that anti-obesity activists think the problem will be solved by putting grocery stories in urban areas is kind of a myth. A grocery store is fine. Farmers markets are great. But food in them tends to be more expensive. Food companies don't advertise frozen vegetables because kids and parents don't buy them, but there is also evidence that kids and parents don't buy them because food advertising primes their hunger and increases their desire for bad foods -- foods that are constructed to make kids feel happy and energetic immediately. Parents have less leisure time to shop. Kids are not encouraged to play outside because of crime rates. And poorer people with lots of material concerns don't have the bandwith to pay close attention to the TV ads that saturate the lives of their kids. And lots of other things. We need to be careful about expectations setting; .everyone can process information the same way. But with an economic and social capital imbalance thrown in, it's terribly hard to blame anyone. I'm harping on social capital because it does provide a different way of looking at the SES and racial disparities. Less social capital is correlated with more stress; there is also a relationship between social capital and the belief that things will get better in the future. The more capital you've got access to, the more optimistic you tend to be, and the more likely you are to think prospectively about health.
And with obesity, we're dealing primarily with children and prevention. Obese adults are not going to lose weight unless they decide to have their stomaches separated from their digestive tracts. Megan is pessimistic about any policy intervention and questions any such intervention from a moral level. But any sensible policy is designed to change the environment
for children, not for adults. It's not as if children are making choices about food and enjoyment in a vacuum. Childhood obesity is fairly contagious: if you've got an obese friend, you are more likely to be obese. The heritability quotient for obesity is .65, which means that obese people tend to produce obese children; whether this is a consequence of genetics, epigenetic factors, pre-natal nutrition -- it's not clear. As kids and adults, obese people tend to cluster with obese people.
There are compelling public policy reasons to try and reduce the rate of childhood obesity. Lectures and hectoring and moral suasion don't work, but changing the environment these kids grow up in might work. Even such a fairly minor intervention as better maternal health habits can influence the likelihood that a child will become obese. Breastfeeding babies reduces the chances for obesity. Kids who sleep more as children will be less obese as adults. Kids who aren't as exposed to pesticides are less likely to become obese.
Without reversing the trendline, obese kids will continue to self-segregate; stigma within their group will be reduced, which is good, but it will grow among thin people, there will be more intergroup tension. John Edwards's two Americas: a fat America and a thin America, coming in about 15 years to neighborhoods near you.