I'm in favor of calorie labeling on menus--unlike some of the more, er, committed libertarians, I don't believe in a very significant right not to know things that make you uncomfortable with your decisions.  (I'm also in favor of encouraging women considering abortions to look at sonograms).  However, I'm pretty skeptical that they'll do much good, for reasons that I outlined last week:  appetite is more powerful than willpower for almost everyone.  If you skip the donut, you'll eat four apples or an extra slice of bread with dinner.  We've required nutritional labelling on food in the supermarket for decades, and this has not exerted any noticeable downward pressure on America's waistlines, even though grocery shoppers are less likely to be having a "splurge".

And this, from Ezra Klein, doesn't make any sense:

Restaurants know that consumers have no effective way of comparing the caloric content of meals. Diners know, of course, that a burger is worse for you than a banana. But eggs cooked in a vat of butter look like eggs cooked in very little butter. A salad with a dressing that adds 600 calories looks like a salad with a dressing that adds 300 calories. People return to restaurants for taste and price and ambiance, because that's what they can measure. So restaurants jack up the caloric content pretty heedlessly.

If menu labeling is passed, however, and consumers exhibit any preference toward relatively less fattening items, that creates an incentive to reformulate those items to be less fattening. California, which recently passed a labeling law for restaurants with more than 20 locations, is seeing this happen. The Macaroni Grill, for instance, just cut its scallop and spinach salad from an astonishing 1,270 calories -- do they grow the spinach in butter? -- to 390 calories. Denny's has slimmed down its Grand Slam breakfast. And the law hasn't even gone into effect yet.

But this is exactly the response we'd expect. The Macaroni Grill's example is a good one. Ordering the spinach and scallop salad is the sort of thing that you'd do if you were watching your calories. But since you didn't actually know how many calories were in the dish, the Macaroni Grill could make it delicious and filling and fatty and you really weren't any the wiser. That made the Macaroni Grill more attractive to healthy eaters even as it was actually tricking them. Now customers will know the caloric content, and so the Macroni Grill reformulated the dish so it's more in line with diner preferences.

If people weren't going to act on the labelling, Macaroni Grill wouldn't be changing its menu.  I doubt they'd be rejiggering their kitchen staff if California passed a law requiring restaurants to publish the name of the workers who made my salad, because that wouldn't change my behavior.

That said, I doubt this is going to have more than a very limited impact on either diner or restaurant behavior.  Obsessing about the calories in your food is an activity largely limited to high SES people.  That's especially true of men:  constant worrying about weight has crept down the female half of the income distribution, but affects perhaps the top 10-20% of males.

Those are the people most likely to . . . order a scallop and spinach salad at Macaroni Grill.  But they're also the most likely to check calories on the website.  And they're the most likely to already be thin.  The people ordering the four-cheese ravioli probably aren't under the misimpression that this is going to make them thin.

Moreover, I bet that after Macaroni Grill reformulates its scallop and spinach salad, more people start ordering heavier entrees, because they suddenly notice that they're still hungry after they eat the salad.  As we've proven over and over and over again with every fake sweetener and imitation fat, you may fool the eyes . . . you may even fool the taste buds . . . but the body knows.  And it almost always gets what it wants in the end.