Lawrence Solomon: The obesity paradox

(June 15, 2012) Despite the immense advances made in medicine, much less is known than not about the myriad influences on our health. The counterintuitive results of a new heart study suggest the human body is far too complex for the one-size-fits-all prescriptions so many are recommended to follow.

Worried that you might have a fatal heart attack some day because your family history shows a tendency to heart disease? Maybe you should consider eating red meat to get your cholesterol up, or taking up smoking, or better yet, do both, and also acquire a couple of other well-known risk factors for heart attacks — high blood pressure and diabetes.

This surmise — the opposite of what you’d hear from your doctor — follows from a startling study of mortality rates among 542,000 hospital patients who suffered their first heart attacks without having had previous cardiovascular disease. The more risk factors that a patient had, the study found, the better the chance of survival.

Someone with all five risk factors that the study looked at had only a 3.6% chance of dying in hospital after an initial heart attack. The chance of dying increased to 4.2% for people with just four risk factors, to 5.3% for those with three risk factors, to 7.9% for those with two risk factors and to 10.9% for those with one risk factor.

What about patients with no risk factors at all? These were the likeliest of all to die — their likelihood of dying in hospital was 14.9%.

Although this study was published in the prestigious Journal of the American Medical Association, although it involved the most comprehensive population to date, and although it was the first to discover how many people supposedly at risk in the general population actually died in hospital following a heart attack — other studies tended to look at sub-populations — your family doctor and most other practitioners are unlikely to act on it, because it runs so counter to the conventional wisdom that they have been dispensing for years. Instead, your family doctor is likely to continue to recommend the tried and possibly untrue measures that may well harm your heart’s health.

So, too, with advice over good and bad cholesterol. Until a month ago, doctors authoritatively told us to increase our HDL, or good cholesterol, believing that HDL protected us from heart attacks. That should soon change, following an authoritative article by Harvard Medical School investigators published in The Lancet showing that people who have high HDL levels due to their genetic makeup, rather than to environmental factors, are no less likely to contract heart disease. Meanwhile, various drugs designed to raise HDL levels have been withdrawn — although they raised HDL levels, they didn’t lower rates of heart disease and some, it turns out, may have increased the chance of strokes.

While dissing good cholesterol, The Lancet study confirms the benefits of reducing LDL, or bad cholesterol, but an ongoing German study that has followed some 30,000 adults since the late 1970s provides some nuance. Yes, LDL at too-high levels is associated with deaths from coronary heart disease, one analysis of its data showed, but at too-low levels LDL is associated with increased cancer deaths. The German study — performed for the International Task Force for Prevention of Coronary Heart Disease and known as the Munster Heart Study — shows a sweet spot midway in the LDL range, at which coronary and cancer deaths are both minimized.

Are there explanations for why so many of these studies provide unexpected results? “There may be multiple explanations for our finding of an inverse association between number of risk factors and mortality,” stated the Journal of the American Medical Association’s hospital heart attack study, before listing them in numbing detail. One explanation is “an apparent obesity paradox … by which overweight or obese patients with established CHD [coronary heart disease] have lower long-term mortality than non-obese patients.” Three of the five risk factors — hypertension, cholesterol and diabetes — are strongly associated with obesity, the authors explain, creating the possibility that these risk factors “confer a ‘protective’ effect” for people experiencing a first heart attack.

The authors recommend more study to determine why they obtained so many counterintuitive results, a recommendation no one would fault. Despite the immense advances made in medicine, much less is known than not about the myriad influences on our health. The human heart, let alone the human body, is far too complex to reduce to five risk factors, and to the one-size-fits-all prescriptions that flow from them, and that so confidently and so often are presented to patients.

Lawrence Solomon is executive director of Urban Renaissance Institute.

This article first appeared in the Financial Post.

To see the surprising study from the Journal of the American Medical Association, click here.   For the Munster Heart Study, showing the sweet spot for bad cholesterol, click here.

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