I did a bit of research into this cold feeling and it seems that people with higher metabolic rates tend to become cold faster while fasting because of the lack of solid foods for the body to use up. It's not a bad thing, just a symptom. I myself have an extremely slow slow slow metabolism and spent the first 21 days of the Master-Cleanse not feeling cold at all, but lately with more exercise I'm feeling cold around 3 pm each day and it lasts until about midnight, so it's an indication that the exercise is causing my metabolic rate to rise slightly. I plan on hitting the gym 6 days a week when I start weaning myself off of the Master-Cleanse and I don't know when that'll be. I'm at day 28 today.