Studies say that we, on average, underestimate the content of restaurant food by 600 calories. They're right.

NYC law requires restaurants with over 10 locations to label their menus with calorie totals. Even at Starbucks, drink calories are not even close to what I would have guessed. My morning Frappuccino is 950 calories and a lesson in data transparency.

How many calories?

One McDonald's Quarterpounder with Cheese Value Meal: burger, large fries, large drink.

Your Guess:

Average Guess:

Actual Calories:

A Lesson in Data Transparency

It's classic paternalism. By mandating that restaurants post calorie counts, NYC nudges New Yorkers to eat healthier. It worked-- a survey found that menu labels affected 82% of New Yorkers' food choices--even I reduced my McGriddle intake. But there have been other changes to my purchasing behavior.

1. I'm less likely to eat healthy, sometimes

Menu labels allow for some simple math. Divide the item prices by their respective calorie totals and you get this:

A $1.99 triple-thick Chocolate Shake buys half my day's worth of nourishment. I'd have to spend $17.96 to get the equivalent number of calories from McSalads. If Iím really hungry and money is tight, whatís the logical choice?

2. Choosing based on averages

Restaurants often place a very expensive item of the menu for perspective. It makes everything else seem cheaper--itís much easier to rationalize a $20 entree if itís right next to one thatís $60.

Similarly, I imagine the same dynamic appears at Dunkin Donuts. If all of the items are 800-1,500 calories, the 700 calorie reduced-fat muffin doesnít seem so bad. And rarely do I grasp the absolute value of caloriesóI just know that 700 calories is better than 800 calories. I never realize that it's 30% of my daily calories.