Most people who quit smoking don't gain a lot of weight, says a study of more than 9,000 adults in Thursday's New England Journal of Medicine. Ex-smokers typically put on 6 to 8 pounds, according to a research team led by David Williamson of the Centers for Disease Control in Atlanta. Men tended to gain less - an average of 6 pounds vs. 8 pounds for women. A small group - 10% of men and 13% of women - eventually gain more than 28 pounds. For reasons that were unclear, blacks, people under age 55 and those who smoke more than 15 cigarettes a day were the most likely to gain significant weight after quitting.