The Concept of CMR

Smoking and Obesity

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When compared to non-obese smokers, obese smokers have a clear reduction in life expectancy (24, 25). Obesity induces several inflammatory markers and cytokines that might contribute to cardiovascular risk. Cigarette smoking, especially in chronic smokers, has also been linked to the induction of several cytokines, such as intracellular adhesion molecule-1 (ICAM-1), tumor necrosis- α (TNF-α), and oxidative stress molecules, while decreasing adiponectin concentrations, inducing insulin resistance, and promoting endothelial dysfunction, which is an early marker of atherosclerosis (26). Furthermore, smoking has also been linked to insulin resistance and low HDL cholesterol levels (27). The figure shows the additional effects of smoking in obese individuals.

Image: Schematic representation of how smoking might add to several mechanisms linking obesity to cardiovascular disease

Image: Schematic representation of how smoking might add to several mechanisms linking obesity to cardiovascular disease

In addition to being a risk factor for arteriosclerosis and ischemic stroke, smoking also increases intra-abdominal (visceral) adipose tissue such that smokers have more of this harmful type of fat compared to non-smokers, even after adjusting for markers of total adiposity (28, 29). These results strongly suggest that body fat distribution can be modified by behavioural factors such as cigarette smoking, despite a well-documented genetic susceptibility to intra-abdominal adiposity (30). This finding is especially important given that intra-abdominal obesity has been reported to be closely associated with the features of the metabolic syndrome increasing the risk of CVD and type 2 diabetes (31).

Reference

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24. Peeters A, Barendregt JJ, Willekens F, et al. Obesity in adulthood and its consequences for life expectancy: a life-table analysis. Ann Intern Med 2003; 138: 24-32.

25. Stevens J, Cai J, Evenson KR, et al. Fitness and fatness as predictors of mortality from all causes and from cardiovascular disease in men and women in the lipid research clinics study. Am J Epidemiol 2002; 156: 832-41.

26. Van Gaal LF, Mertens IL and De Block CE. Mechanisms linking obesity with cardiovascular disease. Nature 2006; 444: 875-80.

27. Reaven G and Tsao PS. Insulin resistance and compensatory hyperinsulinemia: the key player between cigarette smoking and cardiovascular disease? J Am Coll Cardiol 2003; 41: 1044-7.

28. Barrett-Connor E and Khaw KT. Cigarette smoking and increased central adiposity. Ann Intern Med 1989; 111: 783-7.

29. Shimokata H, Muller DC and Andres R. Studies in the distribution of body fat. III. Effects of cigarette smoking. JAMA 1989; 261: 1169-73.

30. Bouchard C, Tremblay A, Després JP, et al. The response to long-term overfeeding in identical twins. N Engl J Med 1990; 322: 1477-82.

31. Després JP and Lemieux I. Abdominal obesity and metabolic syndrome. Nature 2006; 444: 881-7.

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