Effects of dose, gender, and level of physical activity on acute metabolic response to nicotine

The acute thermogenic effect of nicotine was examined in cigarette smokers under conditions of rest and two levels of low-intensity physical activity comparable to that normally engaged in by sedentary adults. Male and female smokers (n = 10 each) each received 0 (placebo), 7.5, 15, or 30 μg/kg nicotine via measured-dose nasal spray once every 30 min for 90 min, with each dose presented on a separate occasion. After each dose presentation, subjects engaged in 10 min of rest or low-intensity activity at 30 or 60 watts (W) using a bicycle ergometer. For males, results indicated that expenditure attributable to nicotine was more than twice as large during 60-W activity compared with rest, while that during 30-W activity was intermediate. For females, expenditure attributable to nicotine was generally similar to that of males during rest and 30-W activity but was significantly lower during 60-W activity, indicating an apparent "inverted-U" relationship with activity intensity. The enhanced of nicotine was specific to energy expenditure, since heart rate showed dose-dependent changes that were generally similar regardless of activity level. These findings confirm a mediating influence of physical activity level on the acute metabolic effect of nicotine, especially in males, and may have implications for explaining individual differences in body weight changes due to tobacco smoking and cessation.