Within the BMI ranges of 30.0 to 34.9, 35.0 to 39.9 or over 40.0, a level classified as morbidly obese in the United States, the percentage of Americans who are now obese was between 32 percent and 34 percent. By way of comparison, Canadian obesity rates ranged between about 25 percent and 27 percent.
Among the most obese, however, the spread was much narrower (5 percent of Americans vs. 3.5 percent of Canadians).
However, the disparity shrank slightly when researchers factored out very high rates of obesity among minority populations in the United States. Among whites in Canada and the United States, Americans were still more overweight, but the gap was smaller (33 percent vs. 26 percent).
The study authors also pointed out that the ethnic mix in each country is different. The American non-white population is comprised mainly of Hispanics and blacks, they noted, who are more likely to become obese than white Americans.
In contrast, Canadian non-whites are composed primarily of East/Southeast Asians, who are less likely to become obese than white Canadians.
Ogden noted that Canada also had a lower obesity rate 20 years ago, compared with the United States. But the obesity rates on both sides of the border have been rising steadily over the past two decades.
What's more, in both countries the trend towards bigger waistlines was spread pretty evenly across all adult age groups, the team found, with the biggest rise in men occurring between the ages of 60 and 74. In women, the biggest rise was seen in the 20-to-39-year-old set.
Ogden stressed that their current effort was simply to get a grip on national trends and the current status quo, rather than an attempt to figure out the underlying causes.
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