A recent study analyzing the eating habits of patients given the option to super-size a meal or snack through visual cues hammers home why the problem with fighting obesity, as I see it, has nothing to do with distinguishing the difference between what's healthy or unhealthy to eat. It's merely a matter of consistently thinking about, and making, the right choices.
Researchers hammered home my point in a number of tests using environmental cues to alter a patient's perception of portion sizes. In one experiment, patients took more or less M&Ms candies depending on the size of the spoon (a quarter-cup ladle or a small spoon) jammed into the bowl.
In another setting, scientists rotated a bowl filled with either 80 mini Tootsie Rolls or 20 packs four times larger than the minis, yet both weighed the same. Consistently, patients generally gravitated to the larger packages or portions without thinking about it.
To be healthier and happier, however, you have to actively choose that path. Eating candies filled with grains and sugars and super-sized portions won't get you there any faster.
There's no better example of how the "super-size" phenomena can ruin your health than Morgan Spurlock's awesome documentary Super Size Me that you can watch for free online.
Psychological Science, Vol. 17, No. 6, June 2006: 521-525
Yahoo News July 30, 2006