The effect of smoking and light activity on metabolism in men

This experiment examined the metabolic effects of smoking during rest and light activity under naturalistic conditions. Thirty-nine male subjects first completed a submaximal graded exercise treadmill test to standardize activity level. Then 3 groups of subjects--smokers smoking (SS), smokers not smoking (SNS), and nonsmokers (NS)--were exposed to 3 stages of rest or 3 stages of light activity with order of rest or activity randomly determined over 2 different days. Energy expenditure was monitored continuously during these sessions. Significant increases in smokers' energy expenditure were observed during light activity when compared with smokers not smoking and nonsmokers. No differences were identified among groups at rest. These findings strengthen the conclusion that smoking or its components contribute to metabolic changes during typical levels of daily activity and suggest a mechanism for the frequently observed relationship between smoking status and body weight.