I've lost almost 60 lbs., and I think that my curves have actually become more pronounced. I've always been kind of "hippy" and that's not going to change (I've got wide-set hips and shoulders). What HAS happened is that I've lost some of the softness that was glomming up around my curves and making me look really doughy. My butt is also actual butt-shaped now and not just kind of a big roundness coming out from my backside, haha!
Now when my waist goes in and my hips come out, I know it's not because I've just piled on the weight on my hips and chest to create sort of an artificial curve (if you will!), but it's because that's my natural shape coming through. I can start to feel my ribs and hipbones and know what my real bone structure is.
I think if you're curvy, you're curvy no matter what, but losing the weight helps you really know your own shape and not whatever shape has been created by being overweight, if that makes sense.
You'll likely lose some of the cup size/band size on your bra, and your hips and butt will get narrower, but your proportions will be the same overall (that is, your waist-to-hip ratio, which is what creates the idea of "curve"). A lot of studies have found that an ideal ratio is 0.7 or so -- that is, for example, a 30-inch waist and a 43-inch hip, OR a 28-inch waist and a 40-inch hip, OR a 26 inch waist and a 37-inch hip (you get the idea).
Do you have to go for ideal? No, of course not. It just might not be your shape. But I think it does show that proportions matter, whether big or small, and you can still certainly be/look curvy even after you lose a bunch of weight
Female, 31 years old, 5'4 1/2" tall
Starting weight 1/4/11 = 215.2 lbs.
Weight 8/29/14 = 180.2 (net: -35.0)
Current mini-goal: 180 lbs.
Next large goal: 165 lbs. by 12/25/2014
Lowest weight: 156.7 lbs.
150.2 lbs. <--- Official "Healthy BMI" weight
Estimated final goal: 130-140 lbs.
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