FWIW, here is my experience with LC and menses:

I started Atkins in March, and did it by the book (except that I refused to quit coffee or booze, but I did cut down on both). In April, I had a slightly heavier than normal cycle, but the cramping was much less than usual. In May, I had very heavy midcycle spotting, almost like a mini-period. I have always had a little ovulation spotting but this was at least 30% more than usual. I skipped my period in June and instead, had spotting for almost the whole month, and the spotting was really severe whenever I exercised heavily (weights or cardio). In July, my period came as usual (cycle was just as if I'd had the period in June)...but I continued to have the bad spotting with exercise. I also had horrendous PMS, felt like I was going mad, and then when the period finally came, I had absolutely excruciating cramps which actually sent me to bed for an entire day, for the first time in my life. The flow was of flooding proportions and lasted almost a week. Painkillers were useless. August, September and October repeated this pattern but with less spotting, less flow less PMS and less pain each time. The cycle that just ended last week is, I would say, back to Normal after five months of weirdness. The usual midcycle spotting and nothing outside of the ovulation time; the usual cramping and the usual flow for the usual amount of days. I am pretty confident that all of this was due to estrogen overload from my body breaking down 35 pounds of fat (so far!). I think my hormones have adjusted now, and I don't expect further problems.

hth

Emily