Why are so many people overweight? Part of the reason, some think, is because they don't have access to, the money to buy, or the desire to eat fresh fruits and vegetables.
That's the idea behind initiatives like the "One more a day pledge" (whose slogan sounds like the pledge-taker might already be choking on carrots: "I pledge to eat ... and help my family eat ... at least ONE MORE fruit or veggie every day." [ellipses sic])
Produce is less calorically dense than grains, meat, and fat, so increasing its consumption might indeed make sense as an obesity-fighting strategy—that is, if eating more fruits and vegetables caused people to compensate by eating fewer cookies and french fries.
Unfortunately, though, we don't really eat that way. We'll have a tossed salad—and then a Chipotle Quesarito. At least, that's what RAND health economist Roland Sturm found in a new paper he co-authored with Ruopeng An, a health policy professor at the University of Illinois at Urbana-Champaign.
Today, people eat about 30 more pounds of vegetables and 25 more pounds of fruit per year than they did in 1970, according to Sturm's calculations.
Unfortunately, they're eating more of everything else, too. The average adult consumed about 2,100 calories in 1970, but in recent years that number has risen to more than 2,500.
Attempts to discourage the consumption of certain macronutrients also don't seem to work. Historically, people have simply eaten less of the forbidden substance and more of the others. During the low-fat craze of the 90s, for example, fat consumption dipped, but carbohydrate intake skyrocketed. And after the Atkins diet took off in 2000, people simply swapped carbs back in for fat.
"Preventing obesity is not about eating more food, regardless of how many nutrients it provides," Sturm and An write, "but consuming less energy or expending more."
Past research on the produce-obesity issue has been mixed: A 2003 study of a large sample of children found that eating more fruits and vegetables had no significant impact on weight. Around the same time, a different study of middle-aged nurses found those who ate more produce were less likely to become obese.
Sturm emphasized that his study is different because it's looking at top-level changes over time, not disparities between groups of people.
A recent Lancet study found that rich and poor countries alike are now struggling with obesity, and that there have been "no national success stories" in stemming the epidemic. So while it's definitely a problem that, say, poor American women tend to be fatter than richer women, another frightening trend is the overall rise of large waistlines over time.