I don't like gaining weight when I stop smoking. Why do I gain weight? What can I do about it?
The short answer is nicotine is a stimulant and all stimulants play a role in appetite suppression and weight loss. The original diet pills were all amphetamine derivatives (stimulants) and were routinely prescribed in the 1950s and 1960s until it became clear they were addictive. Stimulants partly work by increasing the basal metabolic rate, so you burn calories at a faster rate. Thus, when you stop taking them your metabolic rate slows down and you gain weight. Most of the newer medications that are used as weight control pills are also modified derivatives of amphetamines. These include the drug fenfluramine, more commonly remembered as the partner drug known as Fen-Phen that was removed from the market because of heart valve problems. Meridia (the trade name for the drug, sibutramine), instead of causing a direct release of norepinephrine as do the traditional stimulants, blocks the reuptake of norepinephrine and serotonin. Sibutramine is similar in action to some other antidepressant medications, and for that reason it is strongly advised not to use this if you are already taking an antidepressant. There is no real substitute for a strong diet and exercise program, as medications have limited benefits and significant side effects.
The more complicated answer regarding nicotine and weight comes from nicotine's unique actions on various other neurotransmitter and hormonal systems that affect weight, some of which are discussed briefly in Question 83. An additional neurotransmitter system that researchers are working on to aid in weight control may be surprising. Researchers are investigating the use of combination agents, including nicotine replacement therapies and a drug that targets the cannabinoid system. It has long been known that marijuana causes an increase in appetite and weight. A new drug, rimonabant, which is a reverse agonist at one of the cannabinoid receptors (CB1), was approved for use in the European Union (EU) as a weight loss pill. There is some evidence to support its use as a smoking cessation agent in addition to its anorectic effects, but the EU has yet to approve its use in this arena.
Its application to the FDA for use in the United States was withdrawn over concerns about possible adverse effects— most notably depression, suicidal thinking, and self injurious behavior—but also due to the concern that it could lead to neurodegenerative disorders such as multiple sclerosis and Huntington's disease. Still, the fact that a variety of systems are involved in nicotine's effects on appetite and weight point out that this seemingly simple chemical has a very complex and still not well understood effect on the body and brain.
Some diet experts recommend the use of diet patches in addition to a nicotine patch. The ingredients of a typical diet patch are as follows:
Fucus vesiculosus, believed to increase the body's metabolism through stimulation of the thyroid, burn more calories, and enhance digestion.
Guarana, a caffeine-like stimulant that also helps to increase the metabolism while keeping energy levels high.
Hydroxytryptophan (5-HTP), which helps control sweet and carbohydrate cravings by controlling serotonin levels in the brain.
Zinc pyruvate, which assists in the breakdown of fat cells while helping to build lean muscle mass.
Dehydroepiandrosterone (DHEA), which helps the body to manage the intake of calories more efficiently.
Yerba mate, a caffeine-like stimulant with appetite suppressant properties from South America.
Lecithin, which helps to break down fats and cholesterol and balance body weight.
Flaxseed oil, which keeps a balance of essential fatty acids for healthier dieting.
L-Carnitine, which increases the body's fat burning capabilities.
Zinc citrate, an essential mineral often lost when losing weight.
Again, there is no real substitute for a solid diet and exercise program, as they will not only help with the weight gain but will also help with the psychological effects of nicotine withdrawal. If you increase your exercise, drink plenty of fluids, and eat a balanced and healthy diet, you should be able to keep your weight under control and feel better to boot!
I learned quickly that I'd rather diet and exercise later than have a lung disease that I may never survive. My health professional made me aware early on of how serious smoking is compared to dealing with weight gain. Besides, exercising took my mind off smoking, and I could run for over an hour (on a machine) after quitting smoking as compared to running for 14 minutes in the past.
-  A chemical structurally related to amphetamine but it causes an increase in serotonin and decreases appetite. Fenfluramine was originally released in combination with another chemical as Fen-Phen, a diet pill that was taken off the market in 1997 out of concerns that it affected heart valves.