Your Family Physician

Despite being a key cause of heart disease, obesity appears to be protective in a range of cardiovascular problems, a new review concludes [1]. But that doesn't mean people shouldn't try to lose weight, lead author on the paper, Dr Carl J Lavie (Ochsner Medical Center, New Orleans, LA), told heartwire . Indeed, patients who fare the best seem to be obese patients who manage to lose some weight, he said.

"First, obesity is a very strong risk factor and increases all types of heart disease, but second, once you get heart disease, the obese patients do better, so their prognosis is not doomsday," Lavie explained. "In fact, if you have obese patients with congestive heart failure or coronary heart disease or other heart disorders, those patients actually have a pretty good prognosis if they are treated well. But third, the ones who lose weight do even better."

According to Lavie, there is solid evidence to suggest that being overweight or obese may improve survival, not just in heart failure, but also in diseases like hypertension, coronary artery disease, and peripheral artery disease.

"There are a large number of cardiologists who don't even recognize that this is the case, and they are confused about it, too. It is honestly a confusing topic because if obesity is so bad, and it contributes to all cardiovascular risk factors and markedly increases the prevalence of developing heart disease of almost every type, then why, once they get it, do obese patients do better?"

The new review appears in the May 26, 2009 issue of the Journal of the American College of Cardiology (JACC) [1].

Obesity Likely Protects Through Various Mechanisms

The protective effects of excess weight have been best documented in heart-failure patients, where patients with higher body weight or percent body fat have demonstrated better event-free survival. In this setting, says Lavie, extra weight may function much the same way it does with cancer and other chronic diseases, by providing the body with additional fuel to help fight the disease.

Less well known is the relationship between obesity and hypertension, Lavie et al note. While people who are obese do have more hypertension, five papers spanning almost 20 years also point to the fact that obese people with hypertension seem to have lower mortality and/or lower stroke risk, despite less effective blood-pressure control, than do normal-weight people. In this setting, obese patients "may have a better prognosis in part because of having lower systemic vascular resistance and plasma renin activity compared with more lean hypertensive patients," Lavie et al write.

Also incompletely understood is the paradoxical relationship of obesity and coronary and peripheral artery diseases. Obesity is believed to play a causal role in the development of a number of major risk factors for arterial disease, among them hypertension, dyslipidemia, and diabetes, and is believed to be, in and of itself, a risk factor for atherosclerosis. But according to the JACC authors, there is also literature to suggest that overweight and obese coronary heart disease patients have a lower risk for mortality compared with under- and normal-weight coronary heart disease patients who have undergone revascularization procedures. A similar contradictory relationship has been seen in patients with peripheral artery disease.

Speaking with heartwire , Lavie emphasized that the protective effects of excess weight and excess fat likely function in different ways in different diseases. "We know that fat cells do a lot of bad things, but it's certainly conceivable that in advanced disease, the fat cell could have some beneficial effects. There's still a lot that needs to be known about this process."

Weight Loss Still Key

A key new piece of the puzzle that emerged in Lavie et al's review, however, is that weight loss, often touted as a way to reduce cardiovascular risk, appears to be a good thing in spite of the protective effects of extra weight.

"For people who follow this field, these kinds of findings have led them to question whether weight loss is good for heart-disease patients. . . . We found that the patients who do the best are the obese patients who lose weight."

This additional contradiction may be explained in part by the theory that heart disease in obese patients is likely "a different disease" than heart disease in lean people, in whom genetic factors are probably more important. "It may be that the obese person wouldn't have even gotten blocked arteries if [he] hadn't gained 70 pounds over a 30-year period," Lavie said. "The thin person who gets blocked arteries or congestive heart failure or high blood pressure is probably different from the obese patient who got the disease from becoming obese."

For now, he says, it's important particularly for the general public to appreciate that the "protective" effects of obesity in no way provide a rationale for weight gain. "Very clearly," he said, "if no one in our country became overweight or obese, heart-disease rates would go down dramatically."

For physicians, the data today are sufficiently comprehensive for them to encourage their overweight and obese patients to stay motivated to reduce their risk factors. That wasn't always the case, he added. "When people were finding this in their data, five and six years ago, they probably had some trouble getting their papers published, because it didn't make any sense."

The authors do not list any disclosures.

References

1. Lavie CJ, Milani RV, Ventura HO. Obesity and cardiovascular disease. Risk factor, paradox, and impact of weight loss. J Am Coll Cardiol 2009; 53:1925–1932.

Clinical Context

Study Highlights

• Overweight in adults is defined as body mass index of 25 to 29.9 kg/m² and obesity as body mass index of 30 kg/m² or more.
• Indices of obesity that may have more predictive power vs body mass index include body fatness, waist circumference, waist-to-hip ratio, and weight-to-height ratio.
• In both adults and children, obesity has reached global epidemic proportions, which may result in an end to the steady increase in life expectancy.
• Many comorbid conditions have been linked to obesity, including hypertension, type 2 diabetes mellitus, and dyslipidemia.
• In addition to type 2 diabetes, obesity may contribute to other increases in insulin resistance such as glucose intolerance and metabolic syndrome.
• Dyslipidemias linked with obesity include elevated total cholesterol; triglycerides; low-density lipoprotein cholesterol; non-high-density lipoprotein cholesterol; apolipoprotein-B; and small, dense low-density lipoprotein cholesterol particles; and decreased high-density lipoprotein cholesterol and apolipoprotein A-1 levels.
• Obesity increases the risk for cardiovascular abnormalities, including left ventricular concentric remodeling or hypertrophy, endothelial dysfunction, increased systemic inflammation and prothrombotic state, and systolic and diastolic dysfunction.
• Obesity is linked to increased prevalence and severity of cardiovascular diseases including heart failure, coronary heart disease, sudden cardiac death, and atrial fibrillation.
• Noncardiovascular diseases associated with obesity include obstructive sleep apnea, sleep-disordered breathing, albuminuria, osteoarthritis, and specific cancers.
• The importance of obesity in the pathogenesis and progression of cardiovascular disease is confirmed by overwhelming evidence.
• Overall survival duration is decreased in obese patients.
• The obesity paradox refers to the unexpectedly better short- and long-term prognosis, confirmed by evidence from clinical cohorts of patients with established cardiovascular diseases (eg, hypertension, heart failure, coronary heart disease, and peripheral arterial disease) of overweight and obese vs nonoverweight/nonobese people with these diseases.
• Reasons for the obesity paradox are unclear.
• Obese patients with hypertension may have a better prognosis vs those who are lean, possibly because of lower systemic vascular resistance and plasma renin activity.
• Excess body weight may offer some protection against heart failure mortality, perhaps because of more metabolic reserve and protective cytokines and neuroendocrine profiles.
• The review also describes current understanding of the role of weight reduction in preventing and treating cardiovascular disease.
• Despite the obesity paradox, the bulk of evidence still supports voluntary weight loss for prevention and treatment of cardiovascular disease.
• Lifestyle interventions (exercise training and energy restriction resulting in mild weight loss) may reduce risk for type 2 diabetes by nearly 60%.
• Patients with hypertension who lose weight have significant decreases in arterial pressure.
• In heart failure, weight loss may be associated with improvements in left ventricular mass and in systolic and diastolic ventricular function.
• Bariatric surgery in obese patients is associated with short- and long-term reductions in major morbidity and all-cause mortality, particularly related to cancer, diabetes, cardiovascular disease, and long-term lowering of cardiovascular risk.
• More research is needed in the metabolic consequences of obesity, the pathophysiologic effects of obesity on cardiovascular risk factors and disease, and the potential risks and benefits of purposeful weight loss.

Clinical Implications

• Many comorbid conditions have been linked to obesity, including cardiovascular risk factors such as hypertension, type 2 diabetes, and dyslipidemia. Cardiovascular abnormalities associated with obesity include left ventricular concentric remodeling or hypertrophy, endothelial dysfunction, increased systemic inflammation and prothrombotic state, and systolic and diastolic dysfunction.
• Reasons for the obesity paradox, or the unexpectedly better prognosis of obese vs nonobese patients with established cardiovascular diseases, are unclear. Despite the obesity paradox, the bulk of evidence still supports voluntary weight loss for prevention and treatment of cardiovascular diseases.
  

Source : http://cme.medscape.com/viewarticle/703966?src=cmemp