I think that, similarly, I must be a person of variable density. My weight isn't changing, but my size seems to change at random.
This is really all about my jeans. Now, I think women will understand this without any explanation, but for the men in the audience: With the notable exception of the bra, women's clothing sizes bear absolutely no resemblance to the measurements of the woman. Instead, they have an arbitrary scale that isn't even uniform, since in the small numbers it measures odd sizes, but includes even numbers all the way up. Heavier women go into Women's Sizes, denoted with a W after the number - but some manufacturers make clothing in large numbers with no W, for women who are large but not heavy, and some don't. Meanwhile, in pants and skirts, you also have Petite, Regular, and Tall - for petite, read "short". The irony of this is that the lengths aren't consistent, so that a heavy woman who is 5'7" tall, thus slightly on the tall side of average for a woman, may well need to buy petite jeans in a plus size. I speak from experience.
I'm not feeling the need to mention numbers at present, so let's use a new arbitrary scale invented for the purpose, and call the jeans I'm wearing at present size M regular.
Now, a year or so ago, I was wearing a size N instead. I haven't lost any weight since then; in fact by the scale I've gained about ten pounds. However, I've been back down to size M for a while. Recently, and especially today, these jeans have been feeling particularly tent-like, so I decided to go poke around in my dresser, because I thought I had kept old size L jeans.
Much to my surprise, all but one of the pairs of jeans are also size M. This is a pleasant surprise, as it means I can wear them. Right?
Well, they're all M Petites. Two pairs fit slightly better than what I'm wearing now. One pair fit the way I want jeans to fit. Sadly, these are the ones with a frayed seam, which I should just get rid of. The fourth pair, which was a hand-me-down, is a wee bit tight.
The one pair of size L, however, made me feel like an elephant. M petite it is. This means that I'm short and fat. *sigh*
Meanwhile, blouses use the same arbitrary sizing. I keep trying to find tops that fit the way I want, but apparently it is impossible to fit all three of wide shoulders, medium breasts, and a comparatively small waist. In my opinion, my waist is the saving grace of my figure. It makes me curvy instead of just cylindrical, and I think that in combination with good posture, it's what lets me get away with looking less fat than I really am most of the time. However, anything that fits across my shoulders and chest ends up draping like a tent from there down. I believe strongly in tucking in tops, but that tends to make the gapping across the chest even worse.
I'm trying to give in to the theory of tents, even though it saddens me. So, the new blouses I bought the other week are all (on the same scale) size O.
Is it any wonder that my self-image is crap, and I think of myself as a great fat cow?