A study of diabetes patients found that increasing waist size appears to be a stronger predictor of serious heart disease than body weight or body mass index (BMI, the weight-to-height ratio).
"We have known that abdominal obesity is more linked to coronary atherosclerosis [plaque buildup in the arteries] than other forms of obesity," said Dr. Brent Muhlestein, a study author and co-director of research at the Intermountain Medical Center Heart Institute in Salt Lake City.
"We found that left ventricle heart function got worse with progressive waist circumference. The relation between left ventricle function and waist circumference remained highly significant, even after adjusting for body weight," Muhlestein said.
The left ventricle is the heart's primary pumping chamber, and abnormal ventricular function is a common cause of heart disease, including congestive heart failure, the study authors noted.
Muhlestein added that reducing your waist size may reduce your risks.
For this investigation, scientists measured waist circumference, total body weight and BMI in 200 men and women with type 1 or type 2 diabetes. Diabetes can raise heart risks, but patients did not start the study with any symptoms of heart disease.
The researchers evaluated the heart function of study participants by using echocardiography -- a type of ultrasound. They noted that left ventricular function got progressively worse as waist sizes got bigger, with heart decline eventually leveling off at 45 inches of waistline.
The study authors noted that the link between waist circumference and reduced heart function was independent of total body weight and BMI.
Dr. Sarah Samaan, a cardiologist and physician partner at the Heart Hospital at Baylor in Plano, Texas, said these results support previous research indicating that fat in the abdominal area is much more risky than fat elsewhere in the body.
"Abdominal fat produces a wide range of inflammatory substances, and is more highly correlated with heart disease, high blood pressure and diabetes than other types of fat," said Samaan, who was not involved with the study. "We know that heavier people are more likely to have stiffer hearts, which in turn can predispose to heart failure. This study shows us that fat in the abdominal area is especially harmful to heart function."
When compared to men, women in the study in general had better heart function at each increasing level of abdominal obesity. "In general, abdominal obesity had a greater adverse effect on men than women," Muhlestein said.
He said women are advised to maintain a waist size of about 34 inches or less, while men should try to keep their waist circumference at 40 inches or less.
Previous research from the same team of scientists at Intermountain Medical Center Heart Institute and Johns Hopkins Hospital in Baltimore showed that the greater your BMI, the greater your risk of heart disease.
Exercise and diet remain the mainstays of treatment for all obese persons, including those with an apple shape, said Muhlestein. "This study emphasizes, however, that those of us who have an apple shape should perhaps be even more motivated to reduce all of our cardiovascular risk factors, including our waist circumference," he said.
Samaan added that aerobic exercise is the best type of exercise to burn belly fat.
"While crunches may strengthen the abs, they won't necessarily burn abdominal fat," she said. "Also, smokers tend to hold more belly fat, even if their total body weight is normal, so quitting smoking may help."
The report was to be presented Saturday at the annual meeting of the American College of Cardiology, in Chicago. Until published in a peer-reviewed medical journal, data and conclusions presented at meetings are usually considered preliminary.
The American Heart Association has more on how body composition affects heart health.
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