Nope, it’s not thatThis is why we’re fat:

A group of researchers at the UW’s Center for Public Health Nutrition tracked the cost of roughly 380 food items over the course of four years…The price of healthy food—produce and whole grains, among other things—rapidly outpaced the price of items like soda and jelly beans.

“That’s not a good pattern,” said lead researcher Pablo Monsivais. “Already, the foods that are the most nutrient dense are the most costly to begin with. It’s kind of making a bad situation worse.”

food price inflation chart

The chart to the right shows the longer-term food price trends for the US using data from the Consumer Price Index. Since 1985 fats, oils, and sweets have gotten cheaper, after adjusting for inflation, while fruits and vegetables have gotten more expensive. 

The results speak for themselves. The USDA’s Economic Research Service finds that American diets contained 31 percent more calories from fat per day in 2008 than in 1985, and 8 percent more sugar—but fruit and veggie consumption over the period remained basically unchanged. And over the same period US obesity rates simply skyrocketed.

Which all reminds me of this fascinating paper on obesity in the developed world. The authors tried to estimate how much weight gain was due to eating more vs. exercising less, and found that the bulk of our increasing bulk can be explained by higher-calorie diets. And diets, in turn, are largely a function of the economics of food: when fats and sweets are cheap, we eat more of them! Low prices are a powerful inducement for poor eating. Simply offering healthy food choices alongside junk food doesn’t necessarily make us eat more healthfully—in fact, seeing healthy foods on a menu seems to make people feel OK about indulging. Even subsidizing fruits and veggies may not do much to improve eating habits, since many people use the money they save on produce to buy more junk. Which all makes me think that as long as sweets and fats stay cheap, more and more of us are going to feel like we need to go on a diet.