Actually, it's the Metropolitan Insurance Co. weight-height scales, which have been used for years to claim "healthy" weight ranges, but show (in the vaguest way possible) that slightly overweight people live longer than underweight people - ergo, if the weight-height scales were really all that, we wouldn't be pushing people to be severely underweight (which, as a society, we do).

I think what the FA blogs are saying is: Be Healthy. None of them, not Kate Harding's, or anyone else's, are saying lie on the sofa and eat bon bons, they're saying reject societal ideals of thin and be happy and healthy without constantly starving.

...Which is the goal you're trying to reach, so while the words and the m.o. may differ, I think we're trying to reach the same goal, it's simply that mileage may vary. :)