Over the past several weeks, I have quit smoking and significantly increased cardiovascular/aerobic activity. My diet has also changed to plenty more water, fruits and vegetables. Now, over the past couple days, my stool has changed to a dark green color, and I have bowel movements 2-3 times a day. Is this a normal reaction my body is having due to my change in lifestyle that will probably correct itself over time, or is there a possibility there is something more serious going on?