Excess Body Weight and Coronary Artery Disease
if left unchecked, increasing obesity trends will result in a decrease in the upward trend in life expectancy for the US population. Thus, the reduced mortality benefits gained from a projected decrease in tobacco use will be eclipsed and negatively surpassed by the increase in obesity prevalence over the next decade.8
In a study including more than
500,000 US citizens between the ages of 50 and 71, Adams et al.9 reported being classified as either overweight (20–40 % increase) or obese (two- to threefold increase) by BMI at mid-life significantly increased mortality risk in those with no smoking history. Jia et al.10 found the contribution of obesity to quality-adjusted life-years lost has increased by 127 % from 1993 to 2008 in the US. This trend in increasing quality-adjusted life-years lost secondary to obesity is consistent irrespective of sex, race, or geographic location.11
In 1998, the medical
costs attributed to obesity in the US were estimated to be $78.5 billion per year. The medical costs for treating obesity have risen to $147 billion per year in 2008. On a per-person basis, obese individuals spent $1,429 more than normal weight individuals on healthcare in 2006.12
30 20 10 0
Figure 1: Trends in Overweight, Obesity, and Extreme Obesity Among Adults Aged 20–74 Years, US, 1960–2008
40
Overweight
These troubling trends have led to leading health organizations, such as the American Heart Association, to include weight loss as a primary component of public health initiatives.13
Excess body weight is a primary contributor to the increased risk for coronary artery disease (CAD), as well as increasing the likelihood of developing other CAD risk factors. Moreover, once diagnosed with CAD, patients with excess body weight present with a poorer clinical profile in a number of respects. However, once an individual is diagnosed with CAD, there are data to indicate that excess body weight is associated with a reduced mortality risk, a phenomenon defined as the ‘obesity paradox’. The obesity paradox is, of course, counterintuitive and has caused some debate as to how patients with CAD who present with excess body weight should be counseled with respect to weight loss.14 This issue is particularly important for cardiac rehabilitation (CR), where weight loss is considered a primary goal for CAD patients with increased adiposity.15
The present article will address these issues and provide recommendations for weight loss in patients with CAD.
Excess Body Weight and Risk for Coronary Artery Disease
The current body of evidence indicating that excess body weight is a significant and independent risk factor for CAD is overwhelming.2,16 Table 1 lists the risks for type 2 diabetes mellitus (T2DM), hypertension (HTN), and CAD according to BMI and waist circumference (WC).17
One in three men and women in the US who are free of disease but obese at 40 years of age will develop CAD.2
The INTERHEART study,
which assessed CAD risk in 52 countries, identified abdominal obesity as one of the nine key modifiable factors associated with elevated risk.18
Cassidy et al.20 assessed change
A higher BMI in childhood (recorded between seven and 13 years of age) is also associated with an increased risk for coronary events in adulthood for both men and women.19
(mean follow-up 8.9 years) in coronary artery calcification in 443 asymptomatic individuals. Obesity parameters, including WC, the waist:hip ratio (WHR) and BMI were all positively associated with greater progression of coronary artery calcification in those subjects considered to be at low risk for CAD by the Framingham risk equation. An elevated BMI also substantially increases the likelihood of
US CARDIOLOGY
Obese
Extremely obese
Age-adjusted by the direct method to 2000 US Census Bureau estimates, using the age groups 20–39, 40–59, and 60–74 years. Pregnant females were excluded. Overweight is defined as a body mass index (BMI) of 25 or greater but less than 30; obesity is defined as a BMI greater than or equal to 30; extreme obesity is desined as a BMI greater than or equal to 40. Source: CDC/NCHS, National Health Examination Survey cycle I (1960–1962); National Health and Nutition Examination Survey I (1971–1974), II (1976–1980), and III (1988–1994), 1999–2000, 2001–2002, 2003–2004, 2005–2006 and 2007–2008. Source: Ogden and Carrol, 2010.1
Figure 2: Trends in Obesity Among Children and Adolescents, US, 1963–2008
40 30 20 10 0 12–19 years 2–5 years
6–11 years
Overweight
Obese
Extremely obese
Obesity is defined as body mass index (BMI) greater than or equal to sex- and age-specific 95th percentile from the 2000 CDC Gowth Charts.
Source: CDC/NCHS, National Health Examination Surveys II (ages 6–11), III (ages 12–17) and National Health and Nutrition Examination Surveys (NHANES) I–III and NHANES 1999–2000, 2001–2002, 2003–2004, 2005–2006 and 2007–2008. Source: Ogden and Carrol, 2010.4
developing other traditional CAD risk factors such as HTN, T2DM, and dyslipidemia.2,21
the US is paralleled by the rise in obesity.2
In fact, the dramatic rise in the prevalence of T2DM in While the prevalence of
other CAD risk factors has dramatically declined over the last several decades across all BMI categories, Gregg et al.22
reported that a
diagnosis of HTN and T2DM still remains significantly higher in obese individuals. Moreover, obesity is associated with other detrimental factors such as cardiac remodeling, insulin resistance, increased
89
1960–1962
1971–1974 1976–1980
1988–1994 1999–2000 2003–2004 2007–2008
1963–1965 1966–1970
1971–1974 1976–1980
1988–1994
2007–2008 2005–2006 2003–2004 2001–2002 1999–2000
Per cent
Per cent
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