James Hamblin in The Atlantic:
What if nutrition labels told people exactly what calories meant, in practical terms? A bottle of Coke could dole out specific exercise requirements. The calories herein, it might say, are the equivalent of a 50-minute jog. The decision to drink the Coke then becomes, would you rather spend the evening on a treadmill, or just not drink the soda? Some would say that's a joyless, infantilizing idea. The implication that people can't understand calorie counts is unduly cynical. Have a Coke and a smile, not a Coke and a guilt-wail. Others would protest on grounds that it's impossible to make this kind of exercise requirement universal to people of all ages, body sizes, and levels of fitness. Everyone burns calories at different rates. But Sara Bleich, an associate professor at Johns Hopkins Bloomberg School of Public Health, is not among these people. She describes these labels as her dream.
For the past four years, translating nutrition information into exercise equivalents has been the focus of Bleich's increasingly popular research endeavor. Her latest findings on the effectiveness of the concept are published today in the American Journal of Public Health. In the study, researchers posted signs next to the soda and juice in Baltimore corner stores that read: “Did you know that working off a bottle of soda or fruit juice takes about 50 minutes of running?” or “Did you know that working off a bottle of soda or fruit juice takes about five miles of walking?” (And, long as those distances and times may seem, they may even underestimate the magnitude of the metabolic insult of liquid sugar.) The signs were a proxy for an actual food label, but they made the point. They effectively led to fewer juice and soda purchases, and to purchases of smaller sizes (12-ounce cans instead of 20-ounce bottles). Bleich also saw learned behavior; even after the signs came down, the local patrons continued to buy less soda and juice. “The problem with calories is that they're not very meaningful to people,” Bleich told me. “The average American doesn't know much about calories, and they're not good at numeracy.”