Resting Energy Expenditure Response Following Environmental Tobacco Smoke Exposure

Abstract

It has been well-established that active smoking increases the levels of energy metabolism. Specifically, in active smokers resting energy expenditure (REE), exhibits increases equal to 7.2%, when pre - and post - smoking values are compared. Nevertheless, no studies have investigated the effects of passive smoking on energy expenditure. PUrPose: The purpose of this study was to investigate the acute effects of passive smoking on REE. METHODS: The REE of 18 healthy adult non-smokers (9 male; 9 female; age:25.3±3.1 years; height:172.4±10.1 cm; weight: 65±13.7 kg) was evaluated four consecutive times, via indirect calorimetry. The first two REE measurements - separated with a one-hour resting period - were reserved for the control measurements (CREE1 andCREE2). The other two REE assessments were separated by a one-hour resting period while exposed to passive smoke (XREE1 andXREE2) in carbon monoxide concentrations of 15 ppm. Carbon monoxide (CO) concentrations were determined via a gas mixture in a sample chamber using a Horiba (Mexa 311 GE) CO analyzer. Serum cotinine concentrations were obtained before all REE assessments and analyzed via blood chromatography. Analysis of variance (ANOVA) with Bonferroni adjustment was utilized to detect mean differences among REE measurements and adjust for multiple comparisons. RESULTS: Means±standard deviation forCREE1 andCREE2 were 1489.2±285.3 kcal/ day and 1504.3±286.2 kcal/day, whereas forXREE1 andXREE2, 1495.9±291 kcal/day and 1584.9±296.8 kcal/day, respectively. No significant differences were detected betweenCREE1 vs.CREE2 (p > 0.05), andCREE1 vs.XREE1 (p > 0.05), whereas this was not the case forXREE1 vs.XREE2 (p < 0.001) andXREE2 vs.CREE2 (p < 0.05). Serum cotinine concentrations beforeCREE1 andCREE2 were 6.9±3.8 and 6.9±3.6 (p > 0.05) respectively whereas forXREE1 andXREE2 the cotinine concentrations revealed significant differences (7.3±3.6 and 34.0±19.1 respectively, p < 0.001). CONCLUSION: The observed differences betweenXREE1 vs.XREE2 suggest that passive smoking significantly increases energy metabolism in healthy adult nonsmokers. This may be due to immediate immune and or hormonal responses, as exactly clarified in smokers. Further research is required to establish the mechanisms which underline the cause of this increase in REE after passive smoking. This research was supported by the Research Committee of the University of Thessaly.