I get the Muscle Ache alot too I have been working out at the gym 3 days a week and doing the Atkins and the weight is coming off fast. I drink tons of water but I keep getting Charlie Horses. My step dad who has done Atkins and lost alot of weight on he went from like 500 and something to 240 said that I need potassium. You can have nuts on the Atkins and they contain potassium in them and make sure to definatley take a vitamin. I started the induction phase a month ago and lost about 10 lbs and then I went off for a while bad me lol. Then Last Wed. I had an Assesment at the gym I was 246 today I weighed in at 235 so the weight is dropping off.