Hey, I'm also on a fast, with several others as you might have seen. I know you're also doing this for weight loss, but be patient and focus less on weight loss, don't want it to drive you crazy. At 5'6 143 pounds, you are at a healthy weight. By the time you finish your fast, your body will let go off excess weight. That might be a lot, it might not be, unless you go until all fat reserves are gone. But aside from that, underweight or people within normal weight ranges will lose less than their obese or overweight counterparts. I'm here for support if you need it! Fasting is not easy, but is very rewarding!