Except they . . . aren't really that new at all. I remember this advice ("Put down that muffin, fatty! Growing another person is no reason to fall down on your job as a sex object!") from "What to Expect" when I was pregnant for the first time well over a decade ago. This is the usual stuff about how women shouldn't mistake "eating for two" as a license to chow down on donuts and lard-fried pork skins for the entire nine months, as though there is a woman in the entire world who does that. You know how stupid pregnant women are, the argument goes -- give them an inch, and they'll eat Cincinnati.
The biggest problem I see here is that there seems to be a distinct lack of consequences to greater-that-recommended weight gain. The article linked above waves it's hands at cesareans caused by too-big babies ( although I've never seen any science that ties maternal obesity to big babies to C-sections, although I've heard of plenty of doctors harassing women into C-sections because of a too-big baby, only to deliver a four-pound premie, so I'm not overly inclined to believe any "babies too big to birthe" stories) but it doesn't really dwell on it, and it's very clear that they have little to no proof of that problem. The article does discuss (at some length) one possible outcome of "excessive" weight gain in pregnancy: having a harder time loosing the weight after the baby is born.
That's it. The sole bad outcome of gaining more weight than your doctor recommends is you might not get back into your skinny jeans right away. Is that worth considering the caloric content of every mouthful of food for the duration of your pregnancy? "That apple looks really good, but I've already used up my extra 300 calories, so I'd better not."? Seriously? Feh.
Ariel Gore once wrote about how she and a friend used to sit together, planning out how they would get their self-allowed 600 calories a day, and fantasize about how when they got pregnant they would be able to eat all they wanted. Gore's point was that they only considered themselves worth appropriate nourishment once they were gestating children, but as messed up as that view point is, how much worse is it that there is no time in her life that a woman should be free of the pressure to diet and remain visually appealing, even during pregnancy?
In the meantime, here's the diet my midwives recommended when I was pregnant: the Brewer's Diet, which encourages pregnant women to eat a large variety of foods in order to support a healthy pregnancy. It's a huge amount of food (I had a hard time eating that much), but even following it, I was back in my pre-pregancy clothes at six months post-partum. You know why? Because pregnant women might occasionally feel a midnight craving for pretzels and hot-fudge sundae, but are generally going to eat reasonably. And there's no excuse at all for trying to shame them for being incipient fatty fatty two-by-fours when there is apparently no evidence at all that it will hurt anything but their vanity.