Does anybody's weight fluctuate between sizes? And if so, what size do you go with? Do you purchase items on the lower end to keep you 'in check'? Or the larger size to accommodate the rounder days? Or do you simply avoid items that can't accommodate a 10 pound fluctuation? I don't mean that one day you're bloated and the next day you're not--I mean over the course of the year (weather, diet, exercise options, etc). Thanks!