FRIDAY, June 14, 2002 (HealthDayNews) -- A high-tech medical trek into the undeveloped regions of Australia has produced a suggestion that the existing advice about body mass index and the risk of diabetes needs to be adjusted, at least for some Americans.
Body mass index -- weight in kilograms divided by height in meters squared -- is a measure of overweight and obesity. Government guidelines issued in 1998 say that a BMI of 25 or over is unhealthy, increasing the risk of cardiovascular disease and diabetes, among other problems. Before that, a BMI reading of 27 was the official danger point.
But a series of expeditions in which detailed measurements were done on more than 2,600 aborigines in 15 remote Australian settlements found that the risk of diabetes kicked in for BMIs as low as 22, says Mark Daniel, assistant professor of health behavior and health education at the University of North Carolina School of Public Health. He's the lead author of a paper on the expeditions in the journal Diabetes Research and Clinical Practice.
"These results may be relevant for certain populations of North America," says Daniel. For example, he says, "there is some work among African-Americans indicating that those with BMIs below 25 are at higher risk."
Good contacts and good logistics made the Australian study possible, Daniel says. "I lived in Melbourne for a few years and developed connections," he explains. He worked with researchers from the University of Melbourne, the Menzies School of Public Health in Darwin, and the Tropical Public Health Unit of Queensland Health. "We have a long history of working with these people successfully," Daniel says of the aborigines. "It is not easy to get their approval."
The researchers visited and tested aborigines not only in the desert Outback region but also northern lands subject to tropical monsoon rains.
"It was hard to do the work," Daniel says. "You have to transport the laboratory equipment in, get blood samples and do fasting measurements of blood glucose levels, then wait another two hours and test another blood sample."
Overall, the researchers found a 14.9 percent incidence of impaired glucose tolerance, an early warning sign of diabetes, and a 14.8 incidence of diabetes. After adjustment for age and sex, the risk of impaired glucose intolerance was three times greater, and the risk of diabetes was four times greater, for those with BMIs over 22, compared to those with lower readings. Even in the 22-to-25 BMI range, listed as normal by U.S. government guidelines, the risk of diabetes was three times greater.
Daniel is careful to say his finding applies only to the risk of diabetes, not heart disease or other conditions related to obesity. But diabetes itself is an acknowledged risk factor for cardiovascular disease.
The aboriginal study is "an interesting observation," says Matt Petersen, the American Diabetes Association's director of scientific and medical information, speaking from the organization's annual meeting in San Francisco. The problem with applying the information, he says, is that the ADA is working hard just to reach the 50 percent or so of Americans whose BMI is 25 and higher.
"We know that above a BMI of 25, people are at a dramatically increased risk," Petersen says. "Are we going to tell the 90 percent or whatever of Americans above 22 that they are at risk? I'm not sure how that would improve our health message. We're having a hard enough time reaching people as it is."
Nevertheless, he says, the Australian study "helps to point out another metabolic difference between ethnic groups. There could be groups distinctive enough that it might be worthwhile re-categorizing."
What To Do
You can learn about overweight from the National Heart, Lung and Blood Institute, which also has an online BMI calculator.
