On the average, smokers weigh less than nonsmokers, and approximately 80 percent of smokers who quit will gain weight. The average weight gain for smokers who quit is 5 pounds compared to about 1 pound for continuing smokers over the same period, although some quitters (about 20 percent) will gain more than 10 pounds, and a smaller number (less than four percent) will gain more than 20 pounds. Women tend to gain more weight when they quit smoking than men, but the reasons for this are not known.

At least three major issues are important in the relationship between smoking cessation and weight gain. First, many smokers express fear of gaining weight as a reason for not quitting or weight gain as a reason for a relapse back to smoking. The data, however, are not clear that this is the case. Second, a number...