Proportion has some attachment to weight, but it has more to do with your height and the length of your bones and where on your body you carry weight in the first place, as well as where you're delicate. It has to do with the size of your features and how big or small your head is in relation to your body, how straight your shoulders are, etc etc etc.
If I woke up tomorrow at my goal weight (and magically all my clothing had sized down with me), I would look good in the same lines as I do this morning. I would have more options - lots more options - but my basic proportions would stay the same. Still I wouldn't wear calf-length skirts, still I would wear bracelet-length sleeves instead of ultra-long ones, still I would avoid anything labelled "baby doll".
All women should have some idea of their proportions, of the hem lengths that work best on her, the collars that are most flattering, etc. We all have something to showcase, and nearly all of us have something we'd like to hide. This is not body-hatred, this is body-knowledge. Knowing your body and what works on it helps you like your body better.
So if you hear me say something like, "Calf-length skirts matron-ify me" know that I'm not hating on myself. And though I try to put such sentiments more gently with other folks, when I say "that shouldn't belong in your closet" I don't mean that you're unworthy. That piece of clothing simply isn't meant to be part of your life. There's something else for you - something far more fabulous, that will feel like *you*.
Our next problem - and the reason that I sew for myself - is that it can be something of a challenge to find the clothing that ought to be on your body in the stores.
Note: This is written to all those with relatively normal weights - not the morbidly obese and not those so thin that their ribs show through their unbuttoned shirt fronts. But from 20lb below goal weight (or at your modelling gig) to 80 or so pounds above... your arms/legs/shoulders/back are more or less the same. Limbs visually lengthen a bit when they're thinner, you get more waist definition, etc. And obviously you can change the shape of your body if you do heavy body-building. But basically you look like you. Anyway, proportions change **slowly** when they do change, so you should have a chance to keep up!!