To look at Grub's original point, the reason plus size women want their own clothing range is simple. Vanity. We all have it. I wouldn't want to wear something that made me look horrendous, why should they? All women want to dress well, to flatter their shape, irrespective of what that shape is. This is something that all should be able to do. Whether you choose to do it or not is another matter. If the choice is removed from you beacuse someone has decided to stop a clothing range 4 inches below your hip measurement, I think you've every right to shout about it.
As to whether the demand is increasing due to acceptance of weight gain as the consequence of an unhealthy life-style (which I think is Grub's point), that may certainly be true. For every person who is plus-sized despite their attempts to lose weight, there's probably two or three who are that size as a consequence of poor diet and sedentary lifestyle. And they're not attempting to change things. I think we all agree that those who are attempting to control their weight (whether they are succeeding or not) are not the ones that Grub is thinking of.
The human population is changing. Generally we're taller than people 50 years ago, and better nutrition has meant that we have generally grown a bit all round. I love vintage clothes from the 50s, but often find that the body is too short. It's not that I have a peculiarly long body either, simply that at 5'7" (and a bit!) I'm considerably 'longer' than the average height of 5'2" on which garments were fitted then.
BUT...
The statistic of 47% of UK women are size 16 or over is often accompanied by the statement that Marily Monroe was a size 16. Yes, she was. A 1950s size sixteen. Quite different from a modern one. Her measurements are quoted as being 37-23-36 (Studio's Claim); 35-22-35 (Dressmaker's Claim). That BBC article about large waist sizes gives an M&S 16 as being 84cm, or 33". 10" larger than Marilyn's measurement. Yes, nearly a foot larger! A 23" waist measurement doesn't even make it onto their charts (on the M&S
website) - a size 6 has a waist measurement of 24"!! The dressmaker's measurements would, at 89-56-89 make her an M&S 12 bust, 4 waist and 8 hips. The studio measurements make her 14-4-10. By no stretch of the imagination is that anywhere near a modern 16.
Our lifestyles are more sedentary than the 1950s - washing machines, hoovers, dishwashers and cars were luxury items for many people back then, and if you couldn't afford them you burned extra calories doing things the hard way. We don't like to admit we're lazier, and we don't like to admit we're larger. God forbid if anyone then suggested a link between the two!
Better to demand a change in clothing size measurements, than to look at whether we need to reassess our way of life.