The Zip Zip Code

Unusually, this clipping comes from Newsweek, which has a particularly good article on food and place and, although it doesn’t actually mention the idea by name, class too.

Fat Zones: Does where you live influence what you eat? A new study says ZIP codes are surprisingly accurate predictors of obesity.
By Karen Springen
Newsweek
Updated: 6:19 a.m. PT Aug 30, 2007

Aug. 29, 2007 – ZIP codes are more than just a way to deliver mail, they can say a lot about their residents—and not just the ones living in California’s famed 90210. In a study published in the September issue of the journal Social Science & Medicine, University of Washington researchers found that adults living in ZIP codes with the highest property values were the slimmest, and those living in ZIP codes with the lowest property values were the fattest. The findings show that there is significant geographic variation in the obesity problem, and that this variation is very much tied to socioeconomic status and diet. Is this yet another reason for Americans to feel bad about not living on McMansion row? Would people lose weight if they moved to a tonier town? NEWSWEEK’s Karen Springen talked to the study’s lead author, Adam Drewnowski, director of the Center for Public Health Nutrition and professor of epidemiology and medicine at the University of Washington in Seattle. Excerpts:

NEWSWEEK: You looked at 8,803 people in 74 ZIP codes in the Seattle area and found that those living in areas with the highest property values were the thinnest. The inverse was true for those living in the lowest-property-value ZIP codes. Why? Is it because they have less disposable income to spend on healthy food, and they feel less safe going outside and exercising?

Adam Drewnowski: It’s a combination of everything. We’re using where people live as an index of what’s called socioeconomic position, which is usually predicted by education and income and occupation. We think that knowing where people live—not the exact address, but the neighborhood—tells you a lot about poverty and wealth. For most Americans, their biggest single asset is their house. If you live in a nice neighborhood with nice property values, that tells us something about who you are. For example, property values determine taxes, which in turn determine support of schools. The nature of the neighborhood determines access to healthy foods.

NW: Do ZIP codes affect grocery stores?
AD: Take a look at Whole Foods [the organic supermarket] in Seattle, I think now they’re in three locations. One is by the University of Washington, which means education. The second is on the east side, close to Microsoft, which means income and education. The third is downtown. Nice stores set themselves up in areas with buying power. In underserved or disadvantaged poor neighborhoods, you will not get very much other than, in some cases, fast food. People will be buying their groceries at the gas station.

NW: Just how much fatter are people who live in ZIP codes with lower property values?
AD: If we looked at the median prices of residential properties, for each $100,000 of added value, obesity rates go down by 2 percent. In Mercer Island, the median house price is around $1.5 million and the obesity rate is around 5 percent. In the worst areas, in south King County, the median asking price is $270,000 and the lowest asking price is about $10,000 for a manufactured home. The obesity rate there is around 28-30 percent.

NW: Do you think the ZIP code effect would hold true in other parts of the country?
AD: We know it holds in New York City because the department of health there conducted a survey of 10,000 residents in all five boroughs a couple of years ago. Those were not ZIP codes, they were neighborhoods. The department of health noted that if you go from the Upper East Side over to East Harlem, the obesity rates quadruple, from 7 percent to about 28 percent, and the rates of diabetes go up seven times, from 2 percent to 14 percent. You are, in fact, in a different world.

NW: And outside Seattle and New York City?
AD: We are used to thinking that obesity is largely genetic. But if you take a different approach and say obesity and diabetes are predicted by low incomes, neighborhood deprivation and neighborhood poverty, then you have a new angle. For example, looking at incomes in the poor Ninth Ward of New Orleans, it was quite possible to predict that 30 percent would be obese and about 7 percent would be diabetic. No one thought of that. But when the television images came on, everyone noticed that the people left behind were not just poor but obese. In fact, being able to predict obesity and disease by geographic location has implications for public health. There are predictable patterns.

NW: Is it true for kids, not just adults?
AD: I suspect it’s true for kids. The data is for adults.

NW: How did you get the idea to investigate obesity in this way?
AD: ZIP codes aren’t actually the ideal way to look at obesity because they are created for the convenience of delivering mail. The problem is there are no data at any other geographic scale below county level. Certain states sent a behavioral risk-factor survey, administered by the U.S. Centers for Disease Control, to adults in some states, including the state of Washington. We looked at King County. We stopped at ZIP code because there was no finer scale available.

NW: What’s next? Will you look at other ZIP codes?
AD: We would like to look at other geographic areas. The premise here is that maps of health and disease and maps of poverty and wealth are very often one and the same. The point of looking at maps is that if you’re a public-health official, you know where the problem is, so you can target your resources appropriately. You need to know exactly where to intervene, and which neighborhood is vulnerable. That’s why this work is so important.

NW: Will everyone now want to move to rich, thin ZIP codes like Beverly Hills 90210?
AD: That is probably the best way of losing weight!

NW: What about the July study in the New England Journal of Medicine that said someone’s weight gain was associated with weight gain in his or her friends, siblings, spouse and neighbors?
AD: I don’t think Paris Hilton has any fat friends. Most of your friends live in the same area. Or at least in a ZIP code much like yours.

NW: I remember first meeting you nearly 20 years ago, when you were researching whether overweight people had a “fat tooth,” not just a “sweet tooth”—something that drew them to calorie-dense foods. Is there an update to that research, and does it relate to this work?
AD: Yes, it does. I’ve talked about the sweet tooth and the fat tooth, and the kind of connection to this work is very direct. The sweet and high-fat foods are much, much cheaper. After I started studying taste, I started looking at cost. The added sugar and added fat were not only good tasting and satisfying. They were also cheapest. And they’re available even in the lowest-income ZIP codes. The whole thing connects up, like it or not, through money.