I started a running plan (the couch to 5 k plan) 3 full weeks ago, and this month, I'm noticing a longer cycle. I've changed my diet a bit too, but considering I've only lost 2.5 pounds in 3 weeks, I didn't think it was too extreme. Did your cycle change when you started to workout? If so, was it shorter? Longer? Also, I wasn't entirely lazy before, but this is a big change.