Sizing down

A couple of days ago Heidi Klum said something that caused quite a stir in the world of fashion. Asked about size zero she replied "A size zero? I've never heard of that. That didn't exist when I was growing up. When did that start? What does it mean?"
Now while I‘ve never been a fan of Heidi I applaud her for calling out on things so obviously manipulated by the fashion industry to make us feel crappy. Because we‘re talking numbers here, aren‘t we?
I noticed one thing: the cheaper the brand I‘m buying, the bigger my ass is supposed to be.
I‘ve got a couple of skirts in my closet from generally more recognizable designers. Believe or not - apparently the price has shaved a couple of kilos off my thighs and suddenly I‘m wearing an unbelievably comforting size 6 (on the British size scale). Double chocolate cookie, anyone?
But before we gorge ourselves on sweets into proud oblivion we might want to go through the rest of the wardrobe. And that might make you feel really bad about your daily calorie intake.
When I buy Gap or Oasis it‘s already 8.
When I go to Miss Selfridge or Next my behind fills out the British 10 leaving no place for imagination or hope.
And in order not to slip into the one-salad- leaf-a-day-mode I‘ve got to stay away from Mango or Zara for the time being.
What do you think - is there such a thing as vanity (down)sizing? And as a very well paying customer am I entitled to be comforted by a number on the dress tag?
Go figure.