The idea behind calorie counts -- which Obamacare forced chain restaurants to add to their menus -- was that one reason Americans were gaining weight was that prepared food was often deceptively caloric. A favored example was the Macaroni Grill's seared sea scallops salad, which was both exactly the kind of thing you might order if you were watching your weight, and which clocked in at a shocking 1,270 calories.

The theory was that if calorie information was right there in front of them, Americans would, of course, choose lower calorie options. Few considered that the opposite might happen:

That's a photo I took this morning at the McDonald's at D.C.'s Union Station. Most of the menu has small calorie counts. You might not even notice them if you weren't really looking. In fact, as Sarah Kliff found when she reported on the introduction of the calorie counts at another McDonald's, many people don't notice them.

But the calorie count on that advertisement is the single largest type on the whole menu. It draws your eye immediately. It's also one of the highest calorie counts on the whole menu. That's because the high calorie count is, in this case, the selling point.

McDonald's is using the calorie count for the exact opposite purpose public-health advocates intended: It's using high calorie counts to convey what an incredible deal their food is. Look how many calories you get for only $5.69! That's a way better per-calorie deal than pretty much anything else on the board.

Most studies have found little effect from the introduction of calorie counts -- and some studies even hinted at an increase in calories ordered -- so this kind of thing isn't a big surprise. But it's still a nice reminder of how hard it is to get people to change their health habits, and how often well-intentioned interventions end up disappointing.