It is a widely held belief that cigarette smoking causes weight loss. Certainly science supports a role for cigarette smoking in body weight changes. Current evidence suggests that those who smoke cigarettes are protected from weight gain for some reason. A number of reasons for this protection have been suggested, and these generally fall into physiological or behavioural categories. Cigarettes contain nicotine, and nicotine is a central nervous system stimulant. Consumption of nicotine does increase resting metabolic rate, and so regular cigarette smoking could produce physiological changes to metabolism that results in increased energy oxidation. Studies investigating the effects of nicotine have verified that the nicotine could account for the protective effects that cigarettes have on weight gain. This underlying physiological mechanisms has been the focus of the research into cigarette smoking and weight loss, which is understandable in the drug obsessed literature.
However they may be other reasons for the inverse association between cigarette smoking and weight gain. In particular, evidence suggests that those who smoke cigarette may not consume the same levels of snacks as those who do not smoke. The theory here being that those who smoke do so instead of eating food. However, this does not mean that the weight gain is caused by changes to total energy intake. Instead the implication is that the types of snacks consumed by non-smokers are sugary snack, and the increase in fructose consumption decreases insulin sensitivity and this is what leads to weight gain. For example, in one study1 researchers noted that smoking cessation resulted in an increase in the desire for sugary snacks amongst previous female smokers. In particular, the female ex-smokers were particularly drawn to high sugar foods. This may be explained as an attempt by the individual to activate the reward centres of the brain through the use of sugar instead of nicotine.
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