Trust labels much? Maybe you shouldn't. As a recent study conducted by the Journal of the American Dietetic Association suggests, the calorie counts posted on restaurant and prepared food labels can be innaccurate, though not all are.
For example, the label on Lean Cuisine's shrimp and angel-hair pasta claims 220 calories, but these researchers found that it ticked in at 319. How about Wendy's grilled chicken wrap? 260 on the label, 344 calories in their measurements.
The researchers found that it went the other way, too. Domino's thin-crust cheese pizza, while listed at 180 calories, turned out to contain only 141.
Which brings me to the next question: Who cares? I read calorie labels sometimes, but when I do, it would purely be to judge the relative content between foods. I don't weigh it, or even remember it, in absolute terms. I don't get my calculator at the end of the day and account for all that I've consumed. But then, I've never been on a diet.
This, however, brings up an observation. Ever notice that foods that have labels tend to be from fast food chains and/or are processed foods? Maybe that could be a new diet plan: avoid eating anything with a food label. Or just don't eat so freakin' much of it!