Measuring Obesity to Predict a Decline in Heart Health Obesity is one of the key risk factors for cardiovascular disease. This fact is well known. But what's the best way to measure obesity to predict a decline in heart health? One common measure is body mass index (BMI), which is an estimate of your total body fat based on your weight and height. As I've mentioned in previous e-Alerts, a BMI above 25 is considered overweight, and 30 or above indicates obesity. (You can calculate your BMI with the Centers for Disease Control BMI calculator at cdc.gov.) But critics of the BMI point out that many athletes in peak physical shape actually have high BMI numbers because their superior muscle tone adds to their weight. So (goes the argument) Shaquille O'Neill might have a BMI that's in the overweight zone, but he's surely not at higher risk of heart disease because of it. That's a valid point, but it's academic because after we ask all the first-class athletes to leave the room, those of us left behind can feel completely secure in using the BMI to assess weight issues and heart disease risk. In other words, a borderline couch potato shouldn't compare Shaq's BMI to his own unless he's trying to get a laugh. So the BMI is a useful measure. Imperfect, perhaps, but useful. And now that I've defended BMI's honor, it's time to look at a new study published in this month's Lancet that demonstrates how another obesity measurement may be the most accurate predictor of heart attack risk. Last year I told you about the INTERHEART study in the e-Alert "Waking Up is Hard to Do" (9/20/04). The editors of The Lancet called INTERHEART the most "robust" study ever conduced on heart attack risk factors. The international team of investigators that conducted the ten-year INTERHEART research recently finished a new analysis of their data, gathered from more than 27,000 participants among several major ethnic groups in 52 countries. More than 12,400 of these subjects had suffered acute heart attacks. The other subjects - included as controls - were in good health. Incidence of heart attack was assessed in relation to subjects' BMI and waist-to-hip ratios (WHR; a comparison of the circumference of the waist to the circumference of the hips). The results showed a "modest" association between high BMI and heart attack risk. But for waist-to-hip ratio the results were more dramatic. When subjects were grouped from lowest WHR to highest, the risk of heart attack steadily rose as well. Subjects with the greatest WHR were found to be at two and a half times greater risk compared to subjects with the smallest WHR. According to an accompanying article in the Lancet, "This result suggests that previous estimates of the impact of obesity as a cardiovascular risk factor have been too low." Needless to say, a slender hip circumference isn't the problem here; it's all about the abdominal fat. And heart attack risk is only one part of the problem. In the e-Alert "Extra Baggage" (5/18/05), I told you about a 23-year study that showed how excessive abdominal fat raises the risk of factors associated with metabolic syndrome, such as type 2 diabetes, high blood pressure and heart disease. When the INTERHEART researchers first reported on their study last year, they noted that the relative risk for heart attack can be lowered by about 80 percent by doing three things: getting regular exercise, eating plenty of fruits and vegetables, and avoiding smoking. No surprises there, especially with that first item. When it comes to reducing abdominal fat, regular exercise is a must. To get rid of that extra baggage around the middle, you're going to have to get up and get moving. But once you do get moving, there are other ways to help the cause. In the e-Alert "Pretzel Logic" (3/3/05), I looked at a study that showed how a high-glycemic diet (that is; a diet with plenty of simple, refined carbohydrates) is strongly associated with obesity and a tendency to be overweight. And in the e-Alert "Beef 'n' Butter" (4/20/04), I told you how an intake of a fatty acid called conjugated linoleic acid (CLA) may provide some help when it comes to getting rid of excess body fat, especially in the abdominal area. CLA is available in supplement form and from protein-rich dietary sources such as meat and dairy products. This association between protein intake and a trimmer waist was confirmed in a study published in the Journal of Nutrition. Researchers from Canada's Population Health Research Institute recruited more than 600 male and female subjects with a variety of ethnic backgrounds. After subjects completed food frequency questionnaires they were measured to determine WHR. Energy intake from protein averaged less than 16 percent in subjects with the highest WHR. Those with the lowest WHR averaged 17.4 percent energy intake from protein. In their conclusion the authors wrote: "Substituting a modest amount of protein for carbohydrate may reduce abdominal obesity." Sources:
"Obesity and the Risk of Myocardial Infarction in 27,000 Participants from 52 Countries: A Case-Control Study" The Lancet, Vol. 366, No. 9497, 11/5/05, thelancet.com
"Global Study Confirms Best Heart Risk Predictor" The Associated Press, 11/3/05, msnbc.com
"Protein Intake is Inversely Associated with Abdominal Obesity in a Multi-Ethnic Population" Journal of Nutrition, Vol. 135, No. 5, May 2005, ncbi.nlm.nih.gov
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