Abdominal obesity is a major risk factor for cardiovascular diseases. A potbelly indicates that the risk of a heart attack is more even if the rest of the body is skinny as a beanpole.
This new study suggests that the key predictor of risk is the relationship of waist size to the hips. An elevated waist-to-hip ratio predicts an increased risk of heart attack. The study implies that even people who would otherwise be considered safe going by their body-mass index, are found to be at risk using waist-to-hip ratio.
A skinny person with a pot belly would have a low body mass index (BMI) and eventually be classified as having a low risk of heart attack. The researchers insist, it's really the ratio between the measurement around the belly and the circumference of the hips that relates extent of risk.
If the ratio of waist-to-hip is high, then irrespective of the BMI, the risk of having a heart attack is more, according to Arya Sharma, M.D., and Salim Yusuf, M.D., of McMaster University.
'If you have more of a waist line than a hip line, then you're at risk,' Dr. Sharma said in an interview. Sharma is the director of the Canadian Obesity Network.
The Interheart study involved a case-control analysis of acute myocardial infarction , involving 27,098 participants in 52 countries, the investigators reported.
The study had three key findings:
That BMI does not predict heart attack risk, while waist-to-hip ratio does.
It enables one to look at obesity through a new angle as it triples the number of people who are at risk.
The association between increased waist-to-hip ratio and increased heart attack risk found in all countries and cultures is similar.
The waist should be measured roughly between the top of the hip bone and the lower edge of the rib cage without clothing and the hip is measured over light clothing at the widest part of the buttocks.
Dr. Sharma and colleagues study on Interheart data concluded that abdominal obesity is responsible for about 90% of the risk for myocardial infarction around the world, while other risk factors including cigarette smoking, diabetes, poor diet, and lack of exercise account for the rest.
'It just reinforces what we've known for a long time -- the whole apple-shaped, pear-shaped thing,' he said. 'What's new here is that BMI falls right out of the equation.'
'If you just look at crude data, there is some association, but that's just because people with high BMI tend to have a high waist-to-hip ratio,' he said. 'If you correct for other risk factors, BMI essentially gives you no information.'
He confirms, 'there's a smooth increase in risk with increasing waist-to-hip ratio, regardless of BMI.'
'The same rules apply to everybody,' he said. 'Current practice with body-mass index as the measure of obesity is obsolete.'