Skinny people live in a cold, cold world.
I'm the girl that was never cold, well, hardly ever. I skied in single digits. I camped all winter. I went swimming in various rivers and lakes in Kentucky and Tennessee in November. I loved everything about winter.
Since last November, however, I have lost 30+ lbs and I am cold. I am freezing. I've been wearing sweatshirts since September. Before I go anywhere I put all my clothes in the dryer so they'll be warm when I put them on. I've added blankets to my bed and find excuses to use the heating pad.
But, you know what? It's so worth it. :)