March 10, 2011 -- For years, people with a so-called "pear" shape have breathed easier than people with an ''apple'' shape because of their presumed lower risk for heart attack and stroke.
Experts believed that people with apple-shaped obesity, also called central obesity because of excess fat in the belly, had a higher risk for cardiovascular disease than people who are pear-shaped, with excess fat on the hips and buttocks.
Not so, according to a large new study that followed more than 220,000 people in 17 countries.
''Previous studies were suggesting that central obesity was worse compared to general obesity," researcher Emanuele Di Angelantonio, MD, PhD, lecturer at the University of Cambridge, U.K., tells WebMD. ''Actually, this study shows that the two are the same in terms of cardiovascular risk."
“Obesity is an important driver for cardiovascular disease, whatever form it is," he says.
The various measures used to assess obesity -- such as body mass index or BMI, waist circumference, and waist-to-hip ratio -- all perform similarly when used to assess cardiovascular risk, the researchers found.
The study is published online in The Lancet.
Obesity and Heart Disease: Focusing on the Prediction Debate
Over the years, guidelines from national and international organizations such as the National Heart, Lung, and Blood Institute and the World Health Organization have recommended a variety of measures to predict a person's risk of cardiovascular disease.
These recommendations include the obesity measures such as BMI, along with screening tests such as cholesterol, and taking into account other risk factors.
"There has been a lot of controversy" about which recommendation is best, Di Angelantonio tells WebMD.
So Di Angelantonio and his colleagues from the Emerging Risk Factors Collaboration evaluated the medical records of 221,934 men and women in 17 countries who had participated in 58 studies.
Their objective was to analyze individual data and produce reliable estimates of the association of BMI, waist circumference, and waist-to-hip ratio with the onset of cardiovascular disease -- including coronary heart disease, cardiovascular disease, or stroke.
Participants were free of cardiovascular problems at the study start. They were, on average, 58 years old when the studies started and resided in Europe, North America, Australia, and Japan. Each was monitored for nearly a decade.
During the follow-up, there were 14,297 cardiovascular events.
Obesity and Heart Disease: Study Results
''Either BMI [which measures general obesity] or waist circumference or waist-to-hip ratio [a reflection of central obesity] have a similar association with the risk of cardiovascular disease," he says.
They found, too, that if information on blood pressure and cholesterol is available, along with information on risk factors such as diabetes, those are enough to predict cardiovascular disease risk. "You don't need to measure anything else," he says.
The Emerging Risk Factors Collaboration Coordinating Centre is supported by grants from the British Heart Foundation, the U.K. Medical Research Council, and other sources.
Di Angelantonio reports no disclosures, but some co-authors report serving as consultants or receiving lecture payments or research grants from pharmaceutical companies.
Obesity and Heart Disease Prediction: Perspective
Rachel Huxley, DPhil, associate professor at the University of Minnesota School of Public Health in Minneapolis, wrote a commentary to accompany the report.
The new research, she tells WebMD, hopefully will lay to rest which obesity measure is best for predicting risk. "It had been hypothesized that measures of central obesity such as waist and waist-hip ratio would be more strongly associated with cardiovascular risk than measures of global obesity (that is, BMI)," she says. This thinking developed, she says, because in some studies, central obesity measures were more strongly linked with such conditions as type 2 diabetes, which in turn can boost heart disease.
The new research, she says, shows otherwise, suggesting that after adjusting for differences in age, gender, and smoking, ''there is very little difference between the three measures in terms of the strength of the relationship with cardiovascular disease."
The message, she says, is to maintain a healthy body weight -- meaning a BMI of 18.5 to 24.9. Experts say disease risk increases when a woman's waist circumference is over 35 inches and a man's is over 40 inches. To reduce disease risk, a woman's waist-to-hip ratio (waist in inches divided by hips in inches) should be 0.8 or less, a man's 0.9 or less.
Obesity and Heart Disease: Heart Association View
The findings send an important message, but the conclusions may not be the last word, says Tracy Stevens, MD, a spokeswoman for the American Heart Association and cardiologist at St. Luke's Hospital in Kansas City, Mo.
"I think one of the important things the study stresses is that just because you're pear-shaped doesn't mean you aren't going to have heart disease," she tells WebMD.
But Stevens points to many previous studies finding that the more central the fat, the more the risk of cardiovascular disease. "Can we confidently say that this study shows apples and pears are at the same risk? I think there is still credibility to the prior studies."
It is important, she says, not only to look at obesity but also to look at the other risk factors for cardiovascular disease, such as high blood pressure.