Here's what I think might convince a few Americans to eat more healthy food: under the label that shows how many calories a particular food has, the label could also display that amount in pounds—as in pounds that each serving will add to your butt. Basically, divide the number of calories by roughly 3500, and display that amount. That cinnamon roll? .15 pounds. Is it worth increasing your weight by .15 pounds (or counteracting .15 pounds worth of exercise) for a cinnamon roll?
Probably the biggest problem is that people aren't good at extrapolating. .15 pounds isn't, of course, a noticeable amount. But .15 pounds every day for a week is a full pound. A lot of people work really hard to lose a pound a week. I can't say that people would be able to make that jump. Maybe you could divide the number of calories by 500 instead of 3500, and say that if you ate a snack like that every day for a week you'd gain X pounds. In the case of the theoretical cinnamon roll, approximately 1. That'd be more of an in-your-face number. Eat one of these a day for a week, and you gain a pound. Would that motivate people to eat better?
Or, maybe we could, you know, develop more healthy food that doesn't taste terrible. One step at a time, I guess.