Most people do gain some weight when they quit smoking, principally because the nicotine in tobacco acts as an appetite suppressant and increases your metabolic rate. However, the weight gain isn't as great as you may think. It's usually less than 10 pounds, and most people gradually lose this weight within two to five years. Even so, smoking is much more harmful to your health than gaining a few pounds.
I disagree with your belief that you're bound to gain weight when you quit smoking even when you follow strict diet and exercise programs. First of all, surveys have shown that smokers tend to have pretty bad eating habits. They're less likely than nonsmokers to eat fruits and vegetables and, as a result, have a lower intake of fiber and antioxidants. Smokers also typically have higher intakes of total fat, saturated fat, and cholesterol than nonsmokers. Clearly, adopting a healthier diet and increasing your physical activity can help you minimize or even avoid the weight gain that typically occurs when you stop smoking.
If you haven't been exercising, start out by walking. You don't have to carve out a big block of time - just try to fit 30 minutes of walking into your daily schedule at least five times a week. You can do this all at once or in three 10-minute intervals. If you already exercise regularly, add an extra half-hour to your weekly total. Exercise not only burns calories to minimize weight gain, but it will also help reduce any stress you're feeling as a result of not smoking.
As far as diet is concerned, emphasize fruits and vegetables as well as whole grains and healthy protein sources. Avoid foods made with flour and added sugar as much as possible. Make sure you have cut-up vegetables or fruits available for snacks. You'll probably find that your sense of taste and smell will improve once you stop smoking. This change should make fresh, healthy foods more appealing. You can also combat weight gain and the urge to smoke by drinking at least eight glasses of water a day and by regularly practicing a relaxation technique such as deep breathing, yoga, or visualization.
Andrew Weil, M.D.