Addressing the Obesity Paradox in CVD

Las Vegas—Obesity is increasing in epidemic proportions, as 70% of adults in the United States are overweight or obese. Obesity is associated with numerous comorbidities, including major cardiovascular diseases (CVDs). Adverse effects of obesity and cardiovascular health include increased insulin resistance, hypertension, dyslipidemia, abnormal endothelial function, and obstructive sleep apnea.

Despite the adverse association between obesity and CVD, an obesity paradox exists, according to Jane Nelson Worel, MS, ANP-BC APNP, FPCNA, FAHA, who explored the inverse correlation between body mass index (BMI) and mortality found in recent studies during a workshop at the CRS meeting. She cited 2 studies published in 2009 and 2014 in Journal of the American College of Cardiology that examined obesity and CVD. The studies found that although obesity has been implicated as 1 of the major risk factors for most CVDs, including hypertension, heart failure, and coronary heart disease (CHD), evidence from clinical cohorts of patients with established CVDs indicate an obesity paradox because overweight and obese patients with these diseases tend to have a more favorable short- and long-term prognosis.

Hypertension
The obesity paradox has been well-documented in patients with hypertension, heart failure, and CHD. Ms. Worel, internal nurse practitioner, Phase Primary Care for Women, Madison, Wisconsin, continued the session by discussing these 3 risk factors. Obesity increases blood pressure (BP) levels, left ventricular (LV) hypertrophy (independent of BP), and metabolic abnormalities associated with hypertension. She highlighted a study of patients with hypertension and coronary artery disease that found overweight and obese patients had a decreased risk of death, myocardial infarction (MI), or nonfatal stroke compared with patients of normal weight, which was driven by all-cause mortality [Am J Med. 2007;120(10):863-870]. According to another study, in aggregate, although obesity is a powerful risk factor for hypertension and LV hypertrophy, obese hypertensive patients may paradoxically have a better prognosis [J Am Coll Cardiol. 2009;53(21):1925-1932]. This may be due to low systemic vascular resistance and plasma retin activity in obese individuals compared with lean hypertensive patients.

Heart Failure
In patients with chronic heart failure, studies have demonstrated reduced mortality rates in patients with an increased BMI. However, a meta-analysis to examine the relationship between increased BMI and mortality in patients with chronic heart failure found that compared to individuals without elevated BMI, both overweight and obesity were associated with lower all-cause mortality [Am Heart J. 2008;156(1):13-22]. Ms. Worel highlighted a separate study that examined obesity and heart failure mortality in 108,927 decompensated heart failure patients [Am Heart J. 2007;153(1):74-81]. The results showed that a higher BMI was associated with lower cardiovascular and all-cause mortality. For every 5-unit increase in BMI, heart failure was 10% lower.

She cited several reasons that may contribute to the obesity paradox in heart failure. Advanced heart failure is a catabolic state; obese individuals may have more metabolic reserve. Obese individuals have higher BP levels, so they may be able to tolerate more heart failure medicines. Also, higher circulating lipoproteins in obese patients may detoxify lipopolysaccharides that effect inflammatory cytokines.

CHD
Obesity is an independent risk factor for CHD and is strongly related with first premature MI, said Ms. Worel. She referenced an analysis that included 40 cohort studies of >250,000 CHD patients who were followed for 3.8 years [Lancet. 2006;368(9536):666-678]. The researchers found that overweight and obese patients had lower risk of total and cardiovascular mortality compared with underweight and normal weight patients. Potential underlying CHD mechanisms in the obesity paradox include lower prevalence of smoking, greater metabolic reserves, higher BP levels—which means patients may be able to tolerate cardioprotective medications and have a better prognosis—and lower atrial natriuretic peptides.

Studies examining the impact of weight loss in overweight and obese patients remain controversial, said Ms. Worel. For example, some studies have suggested better clinical outcomes, whereas others have indicated no benefits, according to a study [Ochsner J. 2009;9(3):124-132]. However, Ms. Worel highlighted the potential benefits of purposeful weight reduction outlined in another study [J Am Coll Cardiol. 2014;63(14):1345-1354], including:

• Lifestyle interventions with diet and exercise training associated with mild weight reduction (7%-10%) have resulted in reduced prevalence of diabetes and metabolic syndrome
• Overweight and obese patients successful with purposeful weight reduction trend toward lower mortality and a reduction in cardiovascular events
• In hypertension, weight loss is associated with improved arterial pressure and LV geometry
• In heart failure, weight loss, especially with bariatric surgery, has improved LV geometry, systolic and diastolic function, and clinical symptoms
• More large scale studies are needed, but data tends to support purposeful weight loss in patients with CVD and severe obesity (BMI >35 kg/m²)

Clinicians treating obese and overweight patients should underscore the importance of exercise as a contributor to weight loss. She said body weight and fat distribution are improved with exercise. The goal is increased caloric expenditure, which is best achieved with moderate intensity, low impact, long duration, and increased frequency of physical activity. This strategy requires a long-term commitment from patients.

In conclusion, Ms. Worel stated that, in addition to measuring BMI in clinical assessments, clinicians should consider adding waist circumference as a marker of adiposity. Clinicians should also counsel overweight and obese patients regarding purposeful weight loss strategies and encourage regular exercise and less sedentary lifestyles.—Eileen Koutnik-Fotopoulos