I actually have always been "cold-blooded", but it's gotten worse since I lost weight. My mom was always very stingy with the thermometer during Pennsylvania winters, never would go above 68, so I was always cold no matter how many layers I had. (Of course the irony is that now I'm the one trying to control the thermometer (keep it low in the winter/high in the summer) b/c my roommates don't seem to mind outrageously high electricity bills.) I do remember that as a teenager I started making an effort to go for longer walks on the weekends and exercise more, and the exercise always helped make me warmer for a while - I think I have naturally poorer circulation.
Moving to Florida helped me get warmer

, but during the summer everyone always keep their AC cranked to the max here, so I always carry layers that I put on inside, take off outside. During the summer luckily a lot of the socializing is done outdoors, so I can wear cute tank tops and sundresses (but then bare arms get bitten by all the bugs...). In the wintertime (50-60's during the day, 20's-40's at night) all of the rednecks here sit around outside fires in shorts and a t-shirt and I'm the one who's cold in my winter coat. BF makes fun of me, I'm from the north, shouldn't I be the warm one? I'm usually cold all winter long.
But it's been over 3 years since I lost the bulk of my weight, and I'm still freezing. I'm trying to build up my collection of cute jackets, sweaters, etc. I consider it a small price to pay.