Ok, so to shrink, we have to do more exercise and eat more healthily.

But how can you tell when/if you've lost a dress size?
You could go to one shop and be an 8 or a 12 within the same range.

One suggestion is that instead of 'inventing' clothing sizes, clothing labels should have the details of the measurements. For example in a pair of trousers, the label might read:

Inside Leg Length: 30"
Waist: 28"
Hips: 38"

But the complaint about this is women don't want people to know their measurements, they'd rather fool themselves that when they slip into that size 8, it's not a size 12, or 14.