The Risks of Abdominal Obesity
The Risks of Abdominal Obesity
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: Data from the Nurses Health Study revealed that abdominal obesity in females is significantly and positively associated with all-cause and cause-specific mortality and specifically is associated with increased CVD mortality even in normal-weight women.
Source: Li C, et al. Increasing trends in waist circumference and abdominal obesity among US adults. Obesity. (Silver Spring). 2007;15:216-224.
In parallel with the increase in overall body adiposity in the US population, the prevalence of abdominal obesity has increased substantially over the past 15 years and now, more than 50% of US adults have abdominal obesity.1 Accumulating evidence strongly suggests that abdominal obesity is extremely detrimental and is strongly associated with insulin resistance, dyslipidemia, systemic inflammation, metabolic syndrome and certain cancers2,3 independently of overall obesity.4 Waist circumference (WC) and waist to hip ratio (WHR) measurements have been widely used as indirect measurements of abdominal adiposity in epidemiological studies although the association of these measures with mortality had not been widely studied and those that have been reported have been subject to controversy .5-9
Zhang and her colleagues from the Divisions of Epidemiology of the National Institute of Health and Harvard Medical School investigated the relationship between several measures of abdominal adiposity (ie, WC, WHR, and waist-to-height ratio to all cause, cardiovascular disease (CVD) and cancer mortality during 16 years of follow-up of the Nurses' Health Study. In this prospective cohort study of 44,636 women, 3507 deaths were identified including 751 cardiovascular deaths and 1748 cancer deaths during the 16 years of follow-up.10 The anthropometric measures and abdominal obesity were strongly and positively associated with all-cause, CDD, and cancer mortality independent of the body mass index. Elevated waist circumference was associated with significantly increased CVD mortality even among normal-weight women.
Besides the obvious impact on self-esteem and quality of life, the immense personal and economic costs of the obesity epidemic are driven by the obesity-related increases in the risk for developing conditions such as type 2 diabetes mellitus, the metabolic syndrome, CVD, renal disease, arthritis, cancer, asthma and sleep-related disorders. Zhang et al10 extended the already considerable available evidence suggestive of the strong positive relationship between overall obesity and mortality by focusing on the impact of abdominal obesity in the extremely large, well powered Nurses' Health Study. The study results fuel an important debate as to which measure of obesity (ie, body mass index (BMI), WC or WHR) is "better." From a practical point of view, the measurement of waist circumference is simple and most important to each individual patient who is usually well aware of when a pair of pants or jeans are feeling a little tight. Since Zhang has so clearly demonstrated that abdominal obesity is a strong predictor of obesity-related illnesses, it would appears quite clear that monitoring changes in waist size may be as important or perhaps even more important than monitoring changes in weight and BMI. Intra-abdominal adiposity is strongly associated with type 2 diabetes and secretion of adipokines that mediate fat and glucose metabolism. There are multiple factors involved in the development and progression of type 2 diabetes, many of which appear to be influenced by the recently characterized endocannabinoid system. Overactivation of certain endocannabinoid receptors located in abdominal fat tissue and in other central and peripheral sites throughout the body are associated with multiple metabolic morbidities such as hyperglycemia, dyslipidemia and increased food intake, all of which increase the risk of developing type 2 diabetes. It should be recognized that even a modest reduction of intra-abdominal adiposity can significantly improve lipid and glucose levels by decreasing the secretion of harmful adipokines.
Of course, it should be recognized that the Zhang study results may be influenced by the fact that the study population10 consisted primarily of female Caucasian, registered nurses although in a recent study among Chinese women, a strong positive association between WHR and mortality was also observed. Finally, it should be noted that the relationship between mortality and BMI may decline in patients over the age of 7414 as suggested by two studies which included only elderly patients and which revealed an absence of an association between waist circumference and mortality.8,15 It would appear to be doubly important to attempt to curb childhood and adolescent obesity because the risk of obesity in younger populations is twofold and also because these populations have a lifetime during which they can increase their adiposity and during which time the consequences of their obesity can become manifest.
In summary, abdominal obesity in women is significantly and positively associated with all-cause and cause-specific mortality. In addition, increased WC or WHR is associated with increased CVD mortality even in normal-weight women and therefore, maintaining a healthy weight must continue to be a cornerstone in the prevention of chronic diseases and premature death13 and, it would appear that maintaining a healthy or normal waist circumference (ie, under 102 cm. in men and under 88 cm. in women) is important in order to prevent the serious consequences frequently associated with abdominal obesity.
Simple measurement of waist circumference should be encouraged in all medical facilities especially in younger patients in order to help prevent the multiple obesity-related illnesses such as type 2 diabetes, metabolic syndrome, CVD and also death.
1. Li C, et al, Increasing trends in waist circumference and abdominal obesity among US adults. Obesity. (Silver Spring). 2007; 15:216-224.
2. Berg AH, et al. Adipose tissue, inflammation, and cardiovascular disease. Circ Res. 2005;96:939-949.
3. Calle EE, et al. Overweight, obesity and cancer: epidemiological evidence and proposed mechanisms. Nat Rev Cancer. 2004;4:579-591.
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5. Price GM, et al. Weight, shape, and mortality risk in older persons: elevated waist-hip ratio, not high body mass index, is associated with a greater risk of death. Am J Clin Nutr. 2006;84:449-460.
7. Bigaard J, et al. Waist circumference and body composition in relation to all-cause mortality in middle-aged men and women. Int J Obes. (Lond). 2005;29:778-784.
8. Visscher TL, et al. A comparison of body mass index, waist-hip ratio and waist circumference as predictors of all cause mortality among the elderly: the Rotterdam Study. Int J Obes Relat Metab Disord. 2001;25:1730-1735.
9. Lahmann PH, et al. A prospective study of adiposity and all cause mortality: the Malmo Diet and Cancer Study. Obes Res. 2002;10:361-369.
10. Zhang C, et al. Abdominal obesity and the risk of all cause, cardiovascular, and cancer mortality. Circulation. 2008;117:1658-1667.
11. Finkelstein EA, et al. State-level estimates of annual medical expenditures attributable to obesity. Obes Res. 2004; 12:18-24.
12. Xianglan Z, et al. Abdominal obesity and mortality in Chinese women. Arch Inter Med. 2007;167:886-892.
13. Hu FB. Of obesity and mortality: watch your waist, not just your weight. Arch Intern Med. 2007;167:875-876.
14. Stephens J , et al. The effect of age on the association between body mass index and mortality. N Engl J Med. 1998; 338:1-7.
15. Price GM, et al. Weight, shape and mortality risk in older persons: elevated waist-hip ratio, not high body mass index, is associated with a greater risk of death. Am J Clin Nutr. 2006;84:449-460.Data from the Nurses Health Study revealed that abdominal obesity in females is significantly and positively associated with all-cause and cause-specific mortality and specifically is associated with increased CVD mortality even in normal-weight women.
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