Junkfood Science: Obesity Paradox #13 — Take heart

October 07, 2007

Obesity Paradox #13 — Take heart

What is most amazing is how long it has been known that body fat doesn’t cause heart disease or premature death, yet how vehemently people hold onto this belief. “The notion that body fat is a toxic substance is now firmly a part of folk wisdom: many people perversely consider eating to be a suicidal act,” wrote Dr. William Bennett, M.D., former editor of The Harvard Medical School Health Letter and author of The Dieter’s Dilemma. “Indeed, the modern belief that body fat is a mortal threat to its owner is mainly due to the fact that, for many decades, the insurance companies had the sole evidence, and if it was wrong they would presumably have had to close their doors.” That can still be said today, although the obesity interests have since grown considerably larger.

But the evidence that fatness is not especially harmful has been shown from research that dates back to the 1950s — more than a half a century ago. While many remain incredulous, the soundest body of evidence has shown, and continues to show, that being fat is not a risk factor for heart disease or a cause of premature death, even controlling for the effects of smoking or cancer.

Ancel Keys and colleagues, for example, examined 16 prospective population studies in seven countries, as well as actual angiographic and autopsy examinations of 23,000 sets of coronary arteries which found no relationship between body fatness and the degree or progression of atherosclerotic build-up. And the most careful studies ever since have continued to support these findings.

“Before we delve too far into the possible connections between overweight and heart disease, we should look at the evidence to see whether they are as closely linked as they are conventionally assumed to be,” cautioned Dr. Bennett. “Again, we can use major statistical trends to reassure ourselves that fatness cannot be a very important cause of cardiovascular death....”

He wrote that back in 1982, pointing out how the age-adjusted rate of deaths from heart attacks and strokes since the early 1950s had dropped while weights had increased. Biological truths cannot be reversed. These very same findings continue today. As was reported just last month, the health of Americans continues to improve, and heart disease and cancer rates are dropping as weights increase; and the CDC now estimates that today’s children will live longer than ever in our country’s history.

“Detailed epidemiological studies, too, show no impressive connection between obesity and cardiovascular disease,” Dr. Bennett wrote. By that he meant credible, carefully done studies. Junkfood Science readers regularly see how such studies can be manipulated to give the false impression of correlations seeming to show causation by, for example, ignoring confounding factors (like stress, social-economic factors, dieting, and prescription drugs) or using false surrogate endpoints rather than actual clinical disease or deaths. Also, he emphasized, “it cannot be said that fatness in itself causes hypertension...[and] being fat does not, in itself cause diabetes.” Again, those findings continue to hold true today.

Which brings us to a study in the current issue of the American Journal of Medicine, led by cardiologist Dr. Seth Uretsky, M.D., at St. Luke’s-Roosevelt Hospital in New York. By now, we should not be surprised that the media is not reporting on this study, like all the others that go against popular groupthink. These researchers set out to see if the “obesity paradox” of lower morbidity and mortality with increasing body mass index exists with heart disease patients.

The patients were from the INVEST trial, a prospective, randomized international study of 22,576 patients age 50 and older who had hypertension and coronary artery disease. Their heart disease was confirmed and defined as having had a documented heart attack, coronary angiogram with more than 50% stenosis in at least 1 major coronary artery, angina pectoris, or evidence of ischemia on at least 2 different modalities of stress tests (electrocardiogram, echocardiogram, radionuclide scan) that were consistent. The patients received extensive cardiovascular workups in the clinical setting including BMI calculations, and were followed for an average of 2.7 years. The primary outcomes for this study were all-cause mortality, heart attacks and strokes.

Their findings? Compared to ‘normal’ weight patients, the thin patients had 74% higher risk of both death and having a heart attack or stroke, whereas the ‘overweight’ patients had 29% lower risk. But the obese had the lowest risks of all, nearly half that of ‘normal’ weight patients. Only at the very highest BMIs did the risks begin to creep up but they were still less than the overweight and most notably less than the ‘normal’ weight patients. The reverse “J” curve of their graph was amazing similar to that shown earlier this year in a Stanford University-led study of women. The most significant endpoint, all cause mortality, is where the lower risks with fatness were especially striking.

These survival benefits were seen among the fattest, even though they had the highest rates of diabetes, high cholesterol and high blood pressures (even after treatment with medications). They were also younger and less likely to have ever smoked. So, the researchers adjusted for all of the comorbidities and health risk factors and still found that being overweight and obese was associated with lower risks, 1/3 to 1/4 that of patients of ‘normal’ weight. Far more relevant was being thin (52% higher risk); advancing age (a 63% higher risk); smoking (40% higher risk); and comorbidities (diseases themselves, such as kidney disease and congestive heart failure).

They concluded: “Our study is in agreement with previous studies that observed an obesity paradox in patients with previous cardiovascular disease....Our results suggest a protective effect of obesity in [these] patients.”

They noted their results didn’t concur with a few earlier observational studies of the general population, although they failed to reveal the known flaws in those studies or that they have since been discredited or retracted. Even so, they said:

In contrast with these epidemiologic studies, our analysis...among patients with a history of hypertension and coronary artery disease, overweight and class I to III obesity were associated with a decreased risk of morbidity and mortality compared with normal-weight patients, despite less blood pressure control. This finding is consistent with the notion of an “obesity paradox” that has been described in patients with documented cardiac disease (eg, heart failure), patients undergoing percutaneous coronary intervention, and patients with coronary artery disease referred for single photon emission computed tomography.

They proceeded to review the research, such as the Digitalis Investigation Group Trial which found reductions of 12% and 19% for all-cause deaths among the overweight and obese patients compared to normal weight patients. And the 2002 meta-analysis of research on 7,290 patients who’d had percutaneous coronary interventions, showing a 36% and 27% lower risks for death among the overweight and obese patients. Still, in explaining their results and the paradox, they appeared to grapple with bringing themselves to suggest that BMI itself isn’t a risk factor. This was even while they proposed multiple physiological reasons for the higher risks among ‘normal’ weight people, such as: higher-risk coronary anatomy; increased levels of tumor necrosis factor and other inflammatory cytokines (adipose tissue has been shown to produce receptors that neutralize the deleterious effects of the tumor necrosis factor on the heart); the hemodynamics of hypertension (hypertension in obese is characterized by a high cardiac output, an expanded blood volume, and a lower systemic vascular resistance compared to normal weight patients); and that when medical problems themselves are equally well managed, any deleterious effects seen with obesity are negated.

This study actually showed just that. Fat and thin people get sick and get heart disease and other things, but when they receive equally good care for actual health problems, being fat has distinct benefits. The belief that fat kills is simply that... a belief, not good science.

© 2007 Sandy Szwarc

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