Jeremy Piven is explaining his sudden decision to drop out of David Mamet's Broadway production of Speed-the-Plow. "I was losing my balance and my memory," Piven, 43, told Good Morning America on Thursday. "The lights were too bright. I couldn't get enough oxygen." After fainting after work one day, he was admitted to the hospital. Doctors discovered Piven, who says he's eaten no protein other than fish for the last 20 years, had six times the levels of mercury found in a normal person and cautioned that he could have a heart attack if he didn't alter his routine. (Photo: WENN)