Effect of Obesity and Lifestyle on Risk of Acute Coronary Events
Abstract & Commentary
By Harold L. Karpman, MD, FACC, FACP, Clinical Professor of Medicine, UCLA School of Medicine. Dr. Karpman reports no financial relationship to this field of study.
Synopsis: Obesity confers an elevated risk of ACS in subgroups of subjects with both healthy and less healthy lifestyle behaviors. However, adherence to healthy lifestyle behaviors is definitely associated with a lower risk even among obese individuals.
Source: Jensen MK et al. Circulation. 2008; 117: 3062-3069.
The prevalence of overweight (ie, body mass index of 25-29.9 kg/m2) and obesity (ie, body mass index equal to or greater than 30 kg/m2) is increasing in most industrialized countries. In fact, the Centers for Disease Control and Prevention's CDC Morbidity and Mortality Weekly Report of June 18, 2008 reported that 26% of U.S. adults were obese in 2007 compared to only 24% in 2005.1-3 Hypertension, hypercholesterolemia, diabetes and high risk of coronary artery heart disease (CHD) are among the well-established adverse health effects associated with excess weight.4
It has been suggested by some,5-6 but not all,7-9 that physical fitness produced by exercise may improve the CVD risk associated with obesity. However, the effect of changes of other behavioral lifestyle factors on the CVD risk associated with obesity had not been previously clearly evaluated.
Jensen and her colleagues10 therefore decided to follow 54,783 women and men from the prospective Danish Diet, Cancer and Health study who were 50 to 64 years old at baseline and who were free of CVD and cancer. The subjects were followed for a median time of 7.7 years and, after multivariable adjustments were made, each increase in one unit of body mass index was associated with a 5-7% higher risk of acute coronary events (ACS) among both men and women. Overweight and obesity was associated with a higher risk of ACS among both the physically active and inactive, in cigarette smokers and non-smokers, and even among those who adhered more or less to a heart-healthy diet. Finally, obese non-smokers had a somewhat lower risk than did obese smokers, and adherence to a healthy diet was associated with a lower risk of ACS in normal weight subjects but not in obese individuals.
Commentary
In the past, the lack of statistical power, the small numbers of outcome events and the inadequate length of follow-up have been the assumed explanations for study results that have failed to find relationships between obesity, mortality and/or CVD risk. In addition, inconsistencies of findings between studies were probably related to differences in study populations and sampling, the measures of adiposity or obesity which were utilized and the statistical approaches which were used. The Jensen study10 went to great lengths to avoid such pitfalls. BMI is a crude measure of overall obesity and is therefore often not the best predictor of obesity-related outcomes. In fact, there is evidence that measures such as abdominal adiposity are associated with the risk of CVD, independent of overall body adiposity11 and therefore waist circumference measurements are probably a more useful measure of body fat distribution than is BMI.12,13 In addition, published data have clearly demonstrated that low cardiorespiratory fitness is among the strongest risk factors for CVD and related mortality and, in addition, there is evidence that the poor metabolic risk profile of men with low cardiorespiratory fitness is associated with greater visceral adipose tissue accumulation after controlling for BMI.14 In the Jensen study it should be noted that only 8% of study participants were in the healthiest group for all four behavioral lifestyle risk factors (ie, physically active for 3.5 hours/week or more, non-cigarette smoking, high score on the Mediterranean diet scale and light to moderate alcohol intake) and that only 4.1% of the ACS occurred in this group. In addition, the hazard ratio for ACS was 1.65 for the overweight subjects and 2.65 for the obese subjects.10
In summary, obesity confers an elevated risk of ACS in both healthy and less healthy subgroups of lifestyle behavior patterns and, equally important, adherence to healthy lifestyle behaviors was associated with a lower risk even among obese individuals. Dietitians, kinesiologists and behavioral specialists should be recruited to help clinicians achieve optimal management of lifestyle in order to avoid increased CVD risk factors because overweight and obesity are a major cause of CVD morbidity and mortality. From a public health point of view, increases in physical activity along with the establishment of healthy eating habits early in life may be the best and most cost-effective methods to combat obesity and reduce CVD risk, especially because weight gain is progressive as one gets older and because if weight loss is needed and achieved later in life, it is difficult to maintain. It is therefore clearly important that effective weight maintenance and obesity prevention approaches be developed and implemented for all individuals above normal weight no matter at what age these practices are implemented. In other words, it is most important to contain obesity, improve diet, and increase physical activities in everyone but especially in childhood, even in children as young as two years of age.
References
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2. Silventoinen K, et al. Trends in obesity and energy supply in the WHO MONICA Project. Int J Obes Relat Metab Disord. 2004; 28: 710-718.
3. Centers for Disease Control and Prevention's (CDC) Morbidity and Mortality Weekly Report, July 18, 2008.
4. Obesity: Preventing and managing the global epidemic. Geneva, Switzerland: World Health Organization; 2000. Technical report series.
5. Lee CD, et al. Cardiorespiratory fitness, body composition, and all-cause and cardiovascular disease mortality in men. Am J Clin Nut. 1999;69:373-380.
6. Wessel TR, et al. Relationship of physical fitness versus body mass index with coronary artery disease and cardiovascular events in women. JAMA. 2004; 292:1179-1187.
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8. Hu G, et al. Joint effects of physical activity, body mass index, waist-circumference and waist-to hip-ratio with the risk of cardiovascular disease among middle-aged Finnish men and women. Eur Heart J. 2004:25: 2212-2219.
9. Stevens J, 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: 832-841.
10. Jensen MK, et al. Obesity, behavioral lifestyle factors, and risk of acute coronary events. Circulation. 2008; 117: 3062-3069.
11. Snijder MB, et al. What aspects of body fat are particularly hazardous and how do we measure them? Int J Epidemiol. 2006;35:83-92.
12. Barter P, et al. International Day for the evaluation of abdominal obesity (IDEA): a study of waist circumference, cardiovascular disease, and diabetes mellitus in 168,000 primary care patients in 63 countries. Circulation. 2007;116:1942-1951.
13. Canoy D, et al. Body fat distribution and risk of coronary heart disease in men and women in the European Prospective Investigation into Cancer and Nutrition in Norfolk cohort: a population-based prospective study. Circulation. 2007;116: 2933-2943.
14. Arsenault BJ, et al. Visceral adipose tissue accumulation, cardiorespiratory fitness, and features of the metabolic syndrome Arch Int Med. 2007;157:1518-1525.
Obesity confers an elevated risk of ACS in subgroups of subjects with both healthy and less healthy lifestyle behaviors. However, adherence to healthy lifestyle behaviors is definitely associated with a lower risk even among obese individuals.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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