Yesterday, the Sun-Times reported on McDonald's reaction to the new documentary Super Size Me, which shows the effects of eating Mickey D's food exclusively for a month. (The movie opens in Chicago on Friday.) And today, they report that the USDA asserts that low-carb diets are a fad, just like the low-fat diets of the 1990s. (This isn't preventing retailers from making big bucks selling low-carb foods right now, of course; the Food Marketing Institute Convention, currently under way at McCormick Place, features a whole array of new low-carb items, from pizza to salad dressings.)