Yeah, you could be experiencing what's called the "Atkins flu". I remember getting it about a week in or so. My legs really ached. I suspect it's due to fluid and electrolyte fluctuations while the body adjusts to the metabolic changes of switching to fat-burning.
I took some potassium and some extra calcium and magnesium with my daily multvite and it did go away....but who knows? It might have gone away anyway and what I took was inconsequential. And both times for me it only lasted a few days.
It definitely goes away, though.....and I've never had it return, both times I've done Atkins.
It's been my observation that the body does some strange things with fluid balance while on Atkins. I've seemed to have this fairly consistent pattern where my clothes will seem much looser but there's no change on the scale....and my rings are a bit tight. A few days later, after dumping fluid, my rings are looser and I suddenly see a pretty big drop on the scale................rather than a consistent downward trend in only tiny increments like on some of the other types of diets.
But I'd already lost the inches before it showed on the scale....due to some fluid retention. And this seemed to happen repeatedly for me.
But I HAVE stayed on strict induction with no cheating the whole time so not sure if that factored in or to what extent it might have.
Generally, when you dump fluid, you dump some of your electrolytes with it....and this can cause some muscle and leg cramps, etc. Low calcium and some of the other minerals can also cause muscle/leg cramps.
However, even with my repeated fluid dumping episodes, I never got any of the Atkins flu symptoms after the first time at the beginning.
And the good news is, once this passes, you should notice increased energy.
deena