StatsCan Study To Weigh in on Canada’s Obesity Rates
WEDNESDAY, Jan 13 2010 (Canwest News Service) — Dr. Nicolas Christou remembers in 1977 giving a surgical grand rounds — a medical ritual where doctors discuss unusual cases — about a “morbidly obese” patient with a body mass index of 57.
“Nowadays, a BMI of 57 doesn’t even attract our attention,” Christou says.
A BMI of 30 or more indicates obesity. The average BMI in his Montreal surgical practice has increased from the mid 40s in 1995, to 53 today.
“Certainly, a BMI of 105 is not unheard of,” says Christou, a professor of surgery at McGill University and director of the bariatric surgery program at the McGill University Health Centre.
A five-foot, four-inch woman with a BMI of 105 would weigh “somewhere in the 680, 690-pound range.”
When Statistics Canada Wednesday releases results from a unique national survey that took direct physical measurements of about 5,600 Canadians, and compared them to findings from the 1981 Canada Fitness Survey, Christou and others are expecting the results to reflect what they’re seeing in their offices.
They are predicting an overall increase in the prevalence of obesity, “no matter how you define it,” says the University of Alberta’s Dr. Arya Sharma, and an even more dramatic increase in severe or “morbid” obesity.
“If they find things differently, there’s either something wrong with the way we collect statistics, or there’s something wrong with the theories and hypotheses that we’ve all been making about obesity, and the effect on the cardiovascular system and the overall health of the population,” Christou says.
Canada relies mostly on self-reported data, isolated studies and U.S. data to estimate the nation’s health status.
But relying on people to report correctly is a problem. People tend to underestimate their weight, and overestimate their height, for reasons as simple as not having a scale, to the stigma of obesity and the pressure, particularly on women, to conform to “social norms” for slimness.
In 2005, when Statistics Canada for the first time compared self-reported and measured height, weight and BMI for about 4,500 people, self-reported weight was, on average, 2.1 kilograms less than measured weight. The heavier the person, the more likely they were to underestimate their weight, and the bias was greatest among women, who under-reported by an average of 2.5 kilograms, compared with 1.8 kilograms for men.
The new Canadian Health Measures Survey went further. Between March 2007 and February 2009, the survey measured not just the height and weight of Canadians aged six to 79, but also their waist circumference, skin folds on the biceps, triceps, waist and upper back, blood pressure, lung function, strength and flexibility.
Small samples of blood and urine were also collected and tested for chronic and infectious diseases and conditions, such as hepatitis, cholesterol, vitamin and mineral levels and exposures to lead, mercury, pesticides and other environmental exposures.
The study involved in-home interviews and appointments at mobile examination clinics — two customized trailers — that were deployed to 15 collection sites in five provinces: New Brunswick, Quebec, Ontario, Alberta and British Columbia.
Participants were also fitted with a small device powered by a watch battery that recorded their normal physical activity levels for seven days.
The findings, to be released Wednesday, “will provide the first comprehensive estimates of fitness levels of Canadian children and youth aged six to 19, and adults aged 20 to 79, in more than two decades,” according to Statistics Canada. Three more waves of data will be released later this year.
Fatness doesn’t necessarily correspond with fitness. But between 1978-79 and 2004, rates of overweight and obese adolescents aged 12 to 17 more than doubled, from 14 per cent to 29 per cent; their obesity rate tripled, from three per cent to nine per cent.
“We know as a gross measure of unhealthy body weights that there’s been more than a doubling in the incidence of unhealthy body weights,” says Dr. Tom Warshawski, a Kelowna, B.C., pediatrician and chairman of the Childhood Obesity Foundation.
“I’d be very surprised if we don’t see a corresponding decrease in physical fitness.”
He also pointed to the availability and pull of “screen time” products — the Internet, video games and social networking sites.
“There’s more and more appeal and drive to the inactivity than there is to physical activity.
“For all those reasons, it would have to be some magical elixir to be able to make kids more fit now than they were in ’81, with much less physical activity.”