Day 1 for me and I decided that 2 meals would be the order of the day with 2.5 litres of water plus black decaf (which I always have) and black earl grey tea and fruit tea by mid afternoon I have a niggling headache. My calories for the day 900. (I know that it’s over) Having read through the other pages am I suffering from carb flu, I don’t normally get headaches.. Is there anything I can do to get rid of it?