[TRAZ]

Originally Posted by Arch Enemy

When people stop smoking, they usually put on weight. Although this is often a cause for concern, the average weight gain is around 2 to 3 kg although this may be temporary. Although the reasons for weight gain are not fully understood, it may be partly explained by the fact that smoking increases the body's metabolic rate – i.e. the rate at which calories are burned up. In addition, nicotine may act as an appetite suppressant so that when smokers quit an increase in appetite leads to an increase in calorie intake. The effect of nicotine on metabolic rate may also explain why smokers tend to weigh less than non-smokers. Experts believe that one way smoking raises metabolic rate is by stimulating the nervous system to produce catecholamines – hormones which cause the heart to beat faster, thus making the body burn more calories. Nicotine also produces more thermogenesis, the process by which the body produces heat. This too, causes the body to use up more calories.

However, a smoking-induced increase in metabolic rate only accounts for about half the difference in weight between the average smoker and average non-smoker. Another likely mechanism is that smoking alters the body-weight set point, i.e. the weight towards which a person tends to return despite attempts to gain or lose weight. Smoking appears to lower a person’s normal weight and the weight gained on stopping reflects a return to the body’s natural weight set point.

http://www.ash.org.uk/html/factsheets/html/fact10.html

People often replace cigarettes with food to satisfy their need to be putting something in their mouth to keep their minds off of smoking especially right after quitting...Increased caloric intake results in weight gain. Another theory is that the dopamine satisfaction response that a person gets from smoking a cig is also partially induced by food. Basically people try to find a substitute for the satisfaction they get from smoking...And commonly that means eating more.