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Not Just Any Fat: Study Links Abdominal Fat to Stroke Risk

By L.K. Regan

For decades the medical community has warned heavier men about their increased risk for cardiovascular disease and stroke. But new research has revealed that it's not so much what you weigh as where you carry your weight. A study conducted at the University of Heidelberg and published in the August 14 edition of the journal Stroke indicates that abdominal fat is a better predictor of stroke risk than is a standard measure of obesity. The upshot: measure your middle!

Researchers have known for some time that abdominal fat was closely associated with cardiovascular disease—more so than Body Mass Index, or BMI. BMI is the standard method for calculating obesity and is used regularly by the medical community; enter weight and height into a formula, and it will spit out a number that determines how obese you are. (If you're curious about your number, there are many online BMI calculators. Keep in mind that BMI is a simplistic way of looking for obesity; many muscular men, for example, complain that they're BMI suggests they are obese, when in actuality they have low body fat but a lot of muscle). While a high BMI may indicate you are obese, previous studies have shown that it is large amounts of abdominal fat, even with a fairly low BMI, that will significantly increase your risk of heart attack. And now, the German researchers have demonstrated that the same effect holds true for stroke and transient ischemic attacks (TIAs, or "mini-strokes," which are frequent precursors to full-blown strokes).

BMI is a simple calculation involving height and weight. To measure abdominal fat, the German researchers needed a more complex set of data. The study involved 379 participants (238 men and 141 women) with a history of stroke or TIA; these were compared to 758 controls of similar age, sex, and location. For all participants, the researchers measured not only BMI but also the waist circumference, the ratio of the waist to the subject's hip circumference, and the ratio of the waist to the height. By looking at these numbers, scientists were able to get a fairly precise picture of a subject's amount of abdominal fat—such that even subjects with low BMIs might come out on the high end of the abdominal fat calculations, and vice-versa.

Once all calculations were taken, the scientists compared these measurements to the subjects' stroke statistics. The most noticeable conclusion was that, while BMI was initially strongly linked to a history of stroke, that link vanished once other risk factors were taken into account—that is, once the smokers, drinkers, diabetics, and couch potatoes were discounted. But even with these high-risk groups included, the link between high amounts of abdominal fat and cerebrovascular events remained strong. In fact, subjects with large waists—that is, more than 40 inches for men—were at a four times greater risk of stroke or TIA than were average-waisted men. The people with the largest waist-to-hip ratios in the study saw their risk of stroke or TIA jump to eight times that of their hourglass shaped counterparts—again, regardless of BMI or other risk factors, including smoking.

Dr. Tobias Back of Saxon Hospital Arnsdorf in Dresden and an author of the study says that, "While gaining too much weight can present health risks, it's even more dangerous to have the abdominal type of obesity. People should measure their waistline from time to time and avoid the accumulation of abdominal fat." He would like to see doctors get involved as well, specifically by tracking the crucial waist-to-hip ratios: "Physicians should measure patients' waistlines and use the waist-to-hip ratio to estimate stroke risk. World Health Organization-defined categories of WHR [waist/hip ratio] or waist circumference should be used. Doctors should also consider the whole vascular risk profile to minimize or modify all possible factors contributing to coronary heart disease, stroke, and peripheral artery disease." For men, an ideal waist-to-hip ratio is 0.9; for women it is somewhat lower.

What should you do to get the waistline down? Dr. Back recommends vigorous exercise—especially given that most of the physically fit people in the study were in the low-stroke group—but also councils the same diet you would eat for cardiovascular health more broadly: "A Mediterranean diet containing fish and olive oil can lower your risk of coronary heart disease and possibly also lower stroke risk."

For more on the known risks of abdominal fat, and what you can do about it, read the advice of RealJock's nutrition expert, Manuel Villacorta, MS, RD, CSSD, the founder of the interactive weight-management web site Nu4You and the lead nutritionist for RealJock's upcoming Weight-Loss Challenge.