Obesity is on its way to being deadlier than smoking as a cause of cancer, a leading researcher said Friday. Being obese is currently associated with about 14 percent of cancer deaths in men and 20 percent in women, compared with about 30 percent each for smoking, Dr. Walter C. Willett of the Harvard School of Public Health, told the annual meeting of the American Association for the Advancement of Science. "As smoking goes down and obesity goes up it won't be long before obesity is the No. 1 cancer killer," Willett said at a symposium on cancer prevention.