Testing for Obesity: Bye-Bye BMI?

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Testing for Obesity: Bye-Bye BMI?

Waist-to-Hip Ratio May Be Better Test of Heart Attack Risk Than Body Mass Index

By Miranda Hitti
WebMD Medical News

Reviewed By Louise Chang, MD
on Thursday, November 03, 2005

Nov. 3, 2005 -- Get out the measuring tape and shelve the scale, suggest obesity experts in The Lancet.

The best test for obesity -- at least, when it comes to predicting heart attacks -- isn't BMI (body mass index), the researchers write.

Instead, it's the ratio of the measurement of your waist to your hips. It boils down to wider hips and slimmer waists. Larger waists were bad news; larger hips were a plus.

Looking for a loophole? Sorry. The waist-hip ratio was an important sign of heart attack risk in men and women, young and old, in the worldwide study.

BMI Taken Down a Notch

Many people use simple tests to see if they're too heavy. Zippers that won't budge, belts that seem to have shrunk, or spikes in the scale's numbers may tell the story.

Scientists and health experts often use a slightly more complicated obesity test, BMI, which is based on height and weight.

But BMI didn't do as well in a recent global study of heart attacks.

The researchers included Salim Yusuf, DPhil, of the Population Health Research Institute at Canada's McMaster University and Hamilton Health Sciences.

Measuring Obesity to Predict Heart Attacks

The study included more than 27,000 people in 52 countries. Africa, the Americas, Asia, Europe, and the Middle East were represented, along with Australia and New Zealand.

More than 12,400 participants had had a heart attack before the study. The rest had never had a heart attack.

Participants completed surveys on their lifestyle, background, and heart risk factors (including family history of heart disease).

Measurements were done by staff at more than 200 centers, following specific instructions. No one could fudge or claim bulky clothes had added inches to their girth.

Obesity has been shown to raise the odds of having a heart attack.

Best Bet: Waist-Hip Ratio

The waist-hip ratio wasn't just a good indicator of who had had a heart attack. It was more strongly linked to heart attacks than BMI in all eight ethnic groups studied.

BMI was particularly bad at identifying south Asian, Arab, and mixed-race African heart attack survivors, write the researchers.

No matter how the researchers analyzed it, the results didn't change. BMI demonstrated a weaker association to heart attack risk across the board.

Abdominal fat, represented by a wider waistline, has been linked to heart risks. Wider hips may mean bulkier bones and stronger gluteal muscles, write the researchers.

Future studies must be done to validate the importance of the waist-to-hip ratio by assessing how weight loss and shrinking waists affect prognosis, states an editorial in The Lancet.

The editorial was written by Norwegian researchers who weren't involved in the study. They included Charlotte Kragelund of the medicine department at Norway's Akershus University Hospital.


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SOURCES: Yusuf, S. The Lancet, Nov. 5, 2005; vol 366: pp 1640-1649. Kragelund, C. The Lancet, Nov. 5, vol 366: pp 1589-1591. News release, The Lancet.