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Nicotine boosts a busy body's metabolism.

Nicotine boosts a busy body's metabolism

Why do smokers tend to weigh less than nonsmokers and gain weight when they give up the habit?

Contrary to "common knowledge," nonsmokers do not generally eat more than smokers, nor do they exercise less, studies find. Research performed on smokers at rest indicates that nicotine itself can increase basal metabolic rates, meaning smokers burn more calories than nonsmokers during periods of inactivity. But surveys suggest most smokers smoke not while completely at rest, but while performing light activities such as desk work that can increase metabolic rates by two or three times. Unless nicotine's metabolic effects increase proportionally with metabolic rates, its influence on weight might be insignificant.

Now a study in the April 6 NEW ENGLAND JOURNAL OF MEDICINE shows that nicotine's effect on body-fuel consumption do indeed increase proportionally with increases in activity. "These results indicate that the metabolic effect of nicotine may play a greater part in accounting for body-weight differences between smokers and nonsmokers than was previously believed," say Kenneth A. Perkins and his colleagues at the University of Pittsburgh School of Medicine.

The researchers administered a nicotine nasal spray to individuals performing light work -- in this case pedaling an exercise bicycle modified to allow easy pedaling while subjects remain seated in a comfortable armchair. The activity raised resting metabolic rates two to three times.

By analyzing air exhaled, the researchers calculated energy expenditures in the armchair bicylists before and after administering the nasal spray and compared the relative changes with those in controls given placebo nasal sprays. Relative to their baseline bicycle expenditures, individuals in the nicotine group expended considerably more energy than did controls while doing the same amount of work. With nicotine, Perkins says, "it's as if the body is becoming much less efficient in using its stored calories."

While the results may seem discouraging to smokers who'd like to quit without gaining weight, Perkins notes that "walking an extra mile a day should make up for the difference" in metabolic efficiency. And he says smokers would have to gain "well more than 50 pounds" to counter-balance the health risks of continued smoking.
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Author:Weiss, Rick
Publication:Science News
Date:Apr 8, 1989
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