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A new analysis reveals that Canadians had access to about 170 extra calories per day after the first Canada-U.S. free trade agreement — a caloric boost attributed to an increase in highly processed food that flooded into Canada after U.S. trade barriers were removed.

That increase in available calories was estimated to be enough for some Canadians to gain as much as 27 pounds (12.2 kilograms) and could have contributed to rising obesity in Canada.

That's the finding of the UK study that looked at the "natural experiment" created when Canada and the U.S. negotiated the original free trade deal in 1989 — a deal that became a prototype for the North American Free Trade Agreement (NAFTA) and other international trade negotiations.

The study compared Canada with other similar countries and noted that after the Canada-US free trade agreement came into effect in 1989, Canadians had more available calories than the other countries. The only difference — Canada suddenly had a trade deal with the U.S. that lowered trade barriers. In the other countries, trade arrangements did not change.

("Calorie availability" in individual countries is measured by the UN Food and Agricultural Organization and is used as a surrogate measure for a population's food consumption.)

What our study shows is that free trade agreements with the United States can contribute to rising obesity by encouraging a rise in caloric availability and likely intake. - Pepita Barlow, University of Oxford

The analysis can not conclusively determine whether Canadians actually ate those extra calories or if eating those caused weight gain. But Canadian obesity rates more than doubled over the same period and research has shown that obesity resulted from increased caloric intake rather than reduced activity levels.

And because there was no rise in food waste or other factors that explain where all those extra calories went, the authors believe Canadians consumed most of that extra food.

American companies that make processed food and beverages increased their exports to Canada by 102 per cent in the decade after the NAFTA trade agreement, according to the U.S. Department of Commerce.

"What our study shows is that free trade agreements with the United States can contribute to rising obesity by encouraging a rise in caloric availability and likely intake," said study author Pepita Barlow, a sociologist from the University of Oxford in the U.K.

"While not concluding that there is a simple cause-effect between the trade agreement and more calories, more weight gain, and the rise in overweight and obesity in Canada, the study strongly suggests that the trade agreement was one of likely many changes in the Canadian food environment the led to these unhealthy outcomes," said Ronald Labonté​, University of Ottawa epidemiologist who specializes in globalization and public health.

In another study last year, the Oxford University team reported that Canadians were exposed to more high fructose corn sweetener after tariffs were removed following the full implementation of NAFTA by 1998. According to that research, Canadians each faced an extra 42 calories every day from extra sweetener coming into the country from the U.S.

Health Canada is in the midst of a process that will lead to front-of-package labels on highly processed foods. (Kelly Crowe/CBC)

It's a cautionary note about a potential obesity risk from trade agreements that comes just as the Trump administration announced it wants to block any attempts by Canada or Mexico to put warning labels on highly processed foods.

"Yes, the idea of putting limits on the ability of countries to put warning labels and symbols on products is something we are concerned about, " U.S. trade representative Robert Lighthizer confirmed in a committee meeting last week.

Health Canada is in the midst of a process that will lead to front-of-package labels on highly processed foods to alert consumers to products that are high in salt, sugar and fat. That would make Canada the second high-income country after Chile to take that action.

"The international processed food industry, much of it based in the U.S., is afraid that if Chile becomes an example other countries follow, it will create a larger global norm cascade similar to that experienced in tobacco control — from health warnings, to gruesome picture, to plain packaging," Labonté​ said.

Would Canada agree to limit its ability to take public health policy action through food labelling? Labonté​ said it's possible.

"The pressure-cooker final stages of NAFTA re-negotiation being applied by the Trump administration could see Canada trade away this public health protective measure if, for example, concessions in other economic domains of interest to Canada (e.g. auto pact) are improved," Labonté​ said.

But there were reports that Canada's chief NAFTA trade negotiator told reporters that food labels are not on the table.

CBC has asked for confirmation from officials at the Ministry of Health and the Ministry of Foreign Affairs but so far we have not received one.

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