Well-toned hips and a trim waist — not just the pounds you carry — appear to be one of the best protections against heart attacks, according to a study of thousands of people in different countries.
Researchers reported in Friday's issue of The Lancet medical journal that a hip-to-waist ratio is a better predictor of the risk of heart attack for a variety of ethnic groups than body-mass index, the current standard.
Based on weight and height, the body-mass index takes no notice of where fat is or how muscular a person is, said Dr. Arya Sharma, professor of medicine at McMaster University and co-author of the study. An athlete and a couch potato could have similar BMI scores, he noted.
"Irrespective of your BMI, your waist-hip ratio is important."
Previous research has shown that having a potbelly is a better predictor of heart trouble than weight, but most of those studies focused on Europeans or North Americans.
The Interheart study, directed by Dr. Salim Yusuf of McMaster University in Hamilton, Ontario, drew on data from 27,098 people in Europe, Asia, Africa and the Americas, including 12,461 who had suffered a heart attack.
In the new study, the risk of heart attack rose progressively as the ratio of waist size increased in proportion to hip circumference. The 20 percent of the survey who had the highest ratio were 2.5 times more at risk than the 20 percent with the lowest ratio, the study found.
That finding, researchers said, suggested a two-part strategy: trimming the abdomen, and possibly increasing hip size by increasing muscle mass or redistributing fat.
"This clearly will be a better way of identifying people at risk and helping avoid a heart attack," said Dr. Charmaine Griffiths of the British Heart Foundation, who was not involved in the research.
Overall, waist measurements recorded by the researchers were about 90 percent of the hip measurements. People in China scored best at 88 percent, followed by 89 percent in southeast Asia, 90 percent in North America, 92 percent in Africa, 93 percent in the Middle East and 94 percent in South America.
A 30-inch waist and 36-inch hips, for instance, works out to a favorable 83 percent.
The study said the protective mechanism still isn't clear. The authors speculated that hormones may influence waist and hip size, or that there may be important differences in the fat composition in the two areas
Larger hips might also be a marker of overall muscle mass, the study added. If dieting leads to a loss of skeletal muscle mass, that may counteract some of the benefits of simply losing weight, the authors said.
Previous studies have pointed to the benefits of losing weight, but those studies were all based on single well-defined populations, most of European or North American origin, said Charlotte Kragelund and Torbjoern Omland of Akershus University Hospital in Norway. They were not involved in the study.
"The Interheart investigators show that the population risk attributable to waist-to-hip ratio is much larger than the population risk attributable to body-mass index," they wrote in the Lancet.
"This result suggests that previous estimates of the impact of obesity as a cardiovascular risk factor have been too low."
By Robert Barr