Even if you keep strictly to your regular diet and exercise routine when you give up smoking, you are still likely to gain a small amount of weight. That’s because when you smoke, your body burns slightly more calories in order to cope with carbon monoxide and other tobacco toxins. When you quit, your metabolism slows down to more normal levels, which means fewer calories are burned.
And of course, if food is eaten as an oral substitute for smoking and to cope with the stresses of nicotine withdrawal, this will result in some weight gain.
However, rather than worry about small amounts of weight gain, it's best to focus first on giving up smoking, and after you’ve achieved that goal, then worry about giving up your extra pounds. This may sound like advice you don’t want to hear if you are concerned about gaining weight, but, surprisingly, it’s actually your best bet for avoiding the unwanted pounds. The research shows that people who try to focus on both smoking cessation and weight maintenance from the outset usually end up failing at both, and even gain weight. In a 2003 study published by the Association for the Advancement of Behavioral Therapy, women who were encouraged not to worry about their weight only gained an average 5.5 pounds compared with the control group who did focus on weight control and gained an average 11.9 pounds.
Remember, most people only gain between six and eight pounds, so there's no need to delay quitting for fear of gaining a few (easily lost) pounds.