Slate Articles for Chapter 1:
Why Are We Getting So Fat?: A few theories on America's weight problem.
By Steven E. Landsburg
PostedWednesday, May 2, 2001, at 3:00 AM ET
Georgia is the home state of cornbread, barbecue, peach pie, and a whole lot of really fat people—21.1 percent of the state's population, to be exact, is obese. Ten years ago, the cornbread, barbecue, and peach pie were all just as good as they are now, but only 9.5 percent of Georgians were obese. What changed?
Whatever changed, it changed everywhere. Obesity is skyrocketing in every age group, in every race, in both genders, and in every state of the union. The most obese region in the country remains the South—four of the five most obese states are below the Mason-Dixon line—but the spectacular recent growth in obesity is nationwide, led by Georgia but followed by New Mexico, Virginia, California, and Vermont. In 1991, a little over 12 percent of the country was obese; by 1999, it was almost 20 percent. (Click here to see whether you're part of the trend.)
OK, so what's changed in the past decade or so? Well, one thing that's changed is the portion sizes at fast food joints like McDonald's. In 1970, McDonald's offered one size of French fries; today that size is called "small." Eventually, it introduced a new size and called it "large"; today that size is called "medium." There's a new larger large size, but you don't have to settle for that—you can always "supersize it" and go a step beyond large.
So, are we fatter because we're being fed more? Not so fast: Bigger portions don't necessarily translate into bigger meals. When portions were small, you could buy two orders of fries and eat them both; now that portions are enormous, you can buy one supersized order and share it with your family. How much of that goes on? We simply have no idea.
And even if people are eating more fries these days, there's still a which-came-first-the-chicken-tenders-or-the-Egg-McMuffin question: Do big meals cause obesity or does obesity cause big meals? Did McDonald's decide on a whim to fatten us up or did its market research reveal that bigger customers were demanding bigger portions? My money's on the latter. After all, McDonald's was presumably just as greedy in 1970 as it is today, so if we had wanted supersizes back then, we'd presumably have gotten them. That means we still have to figure out why people want to be fatter now than in the recent past.
Well, what else has changed? Here's a thought: Ten years ago, you couldn't read a magazine without walking to the newsstand or at least to the mailbox; today you're reading Slate from the same chair where you work, chat with friends, and do half your shopping. Did Bill Gates make us fat?
The facts suggest otherwise: Obesity tends to be highest in states where computer ownership is lowest, and that's true even after you control for income. Furthermore, increases in obesity tend to be highest in states where increases in computer ownership are lowest. So, the evidence goes against the computers-as-instruments-of-the-devil theory. Instead, computers seem to keep us trim—maybe because they're so fascinating that we forget to eat, or maybe because we burn calories in silent rage every time the system crashes.
What about smoking habits? A lot of people have quit smoking lately, and maybe that's what's making them fat. After all, those who quit often eat more to satisfy their oral fixation. But the numbers tell a different story. It's true that in the 25 states where smoking fell during the '90s, obesity rose 55 percent—but in the 25 states where smoking increased, obesity rose by an even greater 59 percent. Minnesota, where smoking plummeted faster than anywhere else, ranked only 38th in obesity growth. New Mexico, which led the nation in new smokers, ranked second in obesity growth.
So, what else has changed? Incomes have risen, but that cuts both ways: As we get richer, we can afford more food, but we can also afford better quality food and better quality health clubs. On net, there is no statistically significant correlation (in either direction) between changes in income and changes in obesity.
Which brings us back to the same question: What else changed? What happened in the early '90s that could have triggered an obesity epidemic? Did the advent of Rush Limbaugh make obesity stylish? Did the Americans With Disabilities Act make obesity less of a handicap in the job market?
Here's one plausible story: The '90s saw the advent of drugs like Pravachol and Lipitor that can dramatically cut your cholesterol and increase your life expectancy. With medical advances like that, who needs to be thin? Of course obesity is still bad for you—but it's not as bad for you as it used to be. The price of obesity (measured in health risks) is down, so rational consumers will choose more of it.
With the success of the human genome project, even greater advances are just over the horizon, making obesity an even greater bargain. Today's expanding waistlines might reflect nothing more than a rational expectation of future progress against heart disease.
If you don't like that story, here's another: The '90s were the era of low-fat foods. At fewer calories per serving, it makes sense to eat more servings. The net effect can be either an increase or a decrease in weight. For example: Suppose a scoop of ice cream a night would add 10 pounds to your weight, and you've decided that's not worth it, so you don't eat ice cream. Now along comes a low-fat ice cream that allows you to eat two scoops a night and add 10 pounds to your weight. That's a better deal, and a perfectly rational being might well opt for it. So when low-fat foods come along, some people sensibly decide to become fatter. (Other people, equally sensibly, use low-fat foods to become thinner. Therefore, the overall impact of low-fat foods on obesity could in principle go in either direction.)
That's my theory, or rather my pair of theories: The obesity epidemic is caused by some combination of medical advances and low-fat foods. Can some reader do better?
Author Commentary for Chapter 1:
The Readers Weigh In: Your theories on why America is getting fatter
By Steven E. Landsburg
PostedThursday, May 31, 2001, at 9:00 PM ET
Last month in this space I asked Slate readers to help me understand what's going on with obesity—specifically, the explosive growth in obesity over the past 10 years. I'm still digging out from under the excessive weight of the e-mail deluge (several thousand), but here's my preliminary report.
The least helpful contributions are the ones that explain, often in painstaking detail, that obesity is caused by some combination of eating too much and exercising too little. Well, duh. The question is why eating and exercise habits have changed so dramatically at this particular time.
Some readers speculate that nothing has changed other than the definition of obesity. Nice try, but you're wrong: All the numbers in last month's column were based on a fixed definition. (You are obese if your weight in pounds exceeds 4.25 percent of the square of your height in inches.) Others attribute the obesity explosion to the aging of America. Another nice try, but it doesn't fit the facts. Obesity is growing within every age group. There are more obese 40-year-olds today than there were 10 years ago; you can't blame that on aging boomers. (A lot of my e-mail conflated the question "What causes obesity?" with the question "Is obesity a bad thing?" The latter is a separate question, and I plan to come back to it in this column in the near future.)
The angriest e-mail comes from readers who believe they've been duped into eating too many carbohydrates and not enough fat. The Agriculture Department's ubiquitous "food pyramid" recommends six to 11 servings a day of bread, cereal, rice, and pasta—a diet certain, in the minds of my irate correspondents, to trigger insulin reactions that prevent you from burning calories and/or cause you to crave between-meal snacks. At the same time, the food pyramid discourages you from eating the fats that would assuage your hunger. (This circle of ideas, which began with Dr. Atkins' Diet Revolution, is very trendy these days.) So the idea is that the government is handing out exactly the wrong advice, everyone's following it, and nobody's noticed how counterproductive it is. Well. Maybe.
The second-angriest letters come from those who are sure we're getting fatter because of growth hormones in our meat. I won't pretend to know enough science to analyze this one, but I will note that an unusually high fraction of these e-mails are tinged with unmistakable hysteria.
Many of my correspondents surmise that life is busier and more stressful now than 10 years ago, so that we exercise less and eat more haphazardly. That makes sense if indeed life is busier and more stressful, but I have no idea whether that's true. Here's one bit of evidence to the contrary: The average work week is no longer now than in 1990. I'm willing to believe that the average Slate reader's life has gotten busier and more stressful, because the average Slate reader is more likely than the average American to be raising children and in the midst of a demanding career. But it would be rash to overgeneralize.
Quite a few of you mention suburban sprawl, which means more driving, less walking, and less time for meal preparation. I am skeptical, because obesity is growing rapidly in every part of the country but sprawl is still localized. Still, it would be interesting to know whether obesity is growing fastest in the most sprawling areas.
Those were the most common responses. Now for some of the cleverest:
Joseph Taylor makes the simple economic argument that eating is a form of entertainment, and it's gotten cheaper relative to (say) water-skiing; ergo people choose more food and less water-skiing. And he points out that his theory is eminently testable: We could investigate whether obesity is correlated with food prices across geographic regions. Pat Reimann points out that food has gotten not just cheaper but also more varied (consider the uncountable number of new flavors of Ben and Jerry's), which again raises the value of eating relative to other forms of leisure.
Ariel Kaminer starts with my own favorite theory and gives it a novel twist. I argued that medical advances have lowered the health cost of obesity, so people rationally choose to be fatter. Kaminer rejects the rational choice model but points out that the same medical advances have kept a lot of obese people alive, well, and included in the statistics.
Roberta Jupp gives my theory a very different twist by pointing out that just as medical advances make obesity cheaper, so does health insurance. The more heavily you're insured against heart disease, the more likely you are to have that second scoop of ice cream. I love this observation, but I'm not sure that insurance contracts have changed enough in the past 10 years for us to pin all the blame on them.
Besides medical advances, my other theory was that low-calorie foods encourage people to eat more, so their weights might go either up or down, depending on how much more they eat. (Actually, my column referred to "low-fat" foods; several readers correctly pointed out that I should have said "low-calorie," because low-fat and low-calorie are not the same thing.) Raphael Laufer points out an interesting test of this theory: It suggests that we could see movement toward both extremes, as some people use low-calorie foods to indulge themselves and others use them to lose weight. I haven't managed to find numbers that would let me perform this test.
Steven Zara points to Home Shopping Networks, TiVo, cell phones, and cable/satellite TV as new technologies that tend to keep the potato on the couch. Heidi Hirst raises the key follow-up question: How does the obesity explosion correlate with changes in TV viewing hours? And Rusty Bastian asks a great related question: Did obesity increase at a different rate among those who have physically demanding jobs? Sadly, I don't know the answers.
Cindy Shank, Greg Diamond, Paul W. Horn and others point to the advent of Prozac and similar antidepressants. Obesity might be a side effect of such drugs or, more interestingly, maybe Prozac makes you worry less about being obese. But the prize for the most alarming theory goes to Paul Townsend, who writes, "Aliens are force-feeding and fattening us up like geese for liver pate."
There are still several thousand e-mails I haven't gotten to, and I'm sure I'll never get to all of them. If you had a great idea I overlooked, I apologize.