Being cold when you are on a low calorie diet is very common. I have found that one of the most effective ways to combating this is to do squats. I started out with idea of doing the “Squat Challenge” ( you can Google it) because I wanted my butt to be back in its original place (not sure if that will ever happen), but when I started doing the squats, I warmed up immediately and it kept me going for hours. I also did more squats before bed, and I wore layers.