Perhaps the different ethnic makeup of the US is a factor - the American Obesity Association shows that Blacks and Hispanics have significatly higher obesity rates than the white population; anyone got figures for the Canadian obesity rates, to compare these with?
But the quebecois have poutine! That stuff can’t be healthy! 
Just a thought with no hard evidence to back it up - I wonder if obese people are more likely to be thought badly of up here than south of the border? A general aversion to obese people should have some effect on average weight (as in you wouldn’t want to be like one of them). Again, just a thought with no evidence.
Maybe obese people in Canada are ashamed and don’t go out much. Equally valid to explain the OP, eh?
My thoery, at least regarding Toronto and Chicago:
Population density and walkability - Toronto is a very densely populated city, and for the most part neighborhoods are pedestrian friendly. Chicago has some neighborhoods that are filled with high rise apartments – Hyde Park, the Gold Coast – but in Toronto high rise residential buildings are everywhere, even distant suburbs. While single-family houses in Chicago’s suburbs are on normal-sized 1/4 or 1/5 acre lots, Toronto’s sprawl occurs on lots that are 3,000 or 4,000 square feet. A contemporary Toronto-area suburban subdivision will have single family housing at a density comparable to, if not grater than, a 1920s era Chicago bungalow belt neighborhood. Throw high-rises into the mix, and the density is pumped up even more.
That density means it’s more practical to place retail outlets within walking distance of residential areas. In the US. where suburbs are sparse by comparison, most people have to drive to the grocery store; it’s difficult to carry a couple of bags two or three miles to an American tract mansion. Canadian grocery stores are also much smaller than those in the US, which means they can serve smaller populations, and be more conveniently located.
Immigrants - Chicago has a lot of them. Toronto has even more. Much more. Ethnic identity is still very strong in Toronto, and immigrants and first generation Canadians may be eating healthier ethnic diets with relatively small portions, much more so than Canad0an-American food. There is also an abundance of ethnic restaurants where portion size will be smaller; pub grub can be found, but it isn’t as widely available as in Chicago.
Food culture - Consider the Swerski Brothers, of Saturday Night Live’s “Da’ Bears” skit. Chicago-style food is typically very fattening; basically anything that once mooed or oinked ground up and stuck into a sausage casing. Vienna hot dogs, Polish sausage, White Castle sliders, thick-crust pizza, pub grub, and so on - all scream “cChicago!” What do you see when you think of Toronto-style cuisine? The meat-based food culture of American Great Lakes cities just isn’t there.
You ordered a salad and an entree? Bwahahahahahaha… (stumbles off)
You guys talking about portions and meal sizes get real. It’s the Canadian cooking. Can anyone name a Canadian dish that is authentically Canadian, such as Americans have chop suey, hot dogs and pizza?
Gotta second RickJay here. I first went to a Cheesecake Factory within a couple of months of arriving in the US for grad school. I was pretty much appalled at the portion sizes – they were huge. My dining out after that was pretty much limited to ethnic restaurants, which, as others have mentioned, tend to have more reasonable portion sizes.
I think portion sizes are creeping up here in Canada but we’re definitely way behind the US in that department.
That’s true for the central part of the Greater Toronto Area (the City of Toronto itself) perhaps.
But the GTA has just as many McMansions and sprawl as other areas in North America; you just have to go a little further out. The other surrounding cities in the GTA (except for Hamilton) are pretty much all sprawl around small village cores. The City of Mississauga, for example, was synthesised out of pastures and villages forty years ago, hit the suburban boom, and now with a population of 650 000 plus, has basically filled up with sprawl.
It was very amusing to watch Her Eternal Worship* Hazel McCallion (who has been Mayor of Mississauga since before it was formed**, and is now about a million years old***) suddenly announce, just after the last major parcel of open land in the city was bought, that maybe sprawl isn’t such a good thing after all. As a result of this, people are now building fifty-storey condos in an area that was cornfields thirty years ago. (Mississauga: the Shenzen**** of the GTA?)
The actual sprawl construction has moved outward again to the next ring of localities: Brampton, Georgetown, Milton, Stouffville…
We have a lot of big-box stores too. We even lost a couple of enclosed malls to them recently. What has happened in Toronto is big fullservice food stores opening downtown to serve the forest***** of fifty-storey residential buildings going in around the financial district.
I won’t argue with that; we’re mostly immigrants now. Dunno how it reflects on portion size though… though I have notices an enphasis on what I call “food art” lately: artfully sprinkling decorative condiments around the edges of the plate, for instance. I suppose that sould be said to imply that the edges of the plate are visible…
I’m not sure that we have a “Toronto” cuisine yet. Things are still in flux. Check back in thirty years. 
[sub]*Yes, Canadian mayors are addressed as “Your Worship”. So are judges.
** She was mayor of the village of Streetsville before Mississauga was formed. Streetsville is now just a granularity in the Mississauga sprawl.
*** At least eighty.
****Then again, you could say that Shenzen is the Mississauga of Hongkong…
*****And I’m not kidding. There are at least a dozen towers over thirty storeys high within a kilometer of the centre of downtown. And then there’s the battle between The Donald and The Local Boy for the tallest hotel/residential tower in the city. At eighty storeys, they will be taller than any of the office towers. [/sub]
Pizza is Italian, arriving in America some 75 years after the first pizzeria in Naples. It’s debatable whether chop suey actually originated in the US, or in Toisan, China. The only verifiably American dish you list there is the hot dog.
Tortierre and poutine are French Canadian dishes, and you can find butter tarts and Nanaimo bars in bakeries across the country. None of these, of course, can be used to justify the lower obesity rates, since they’re hardly good examples of healthy nutrition.
That’s a bit of a woosh there. YPOD was being ironic, listing foods that are “imported,” (leaving aside that chop suey is probaby an American dish.)
Hot dogs aren’t native to the United States, either, which is part of his joke. That they’re properly called “weiners” and “frankfurters” is a bit of a hint that the concept is a European import. Maybe Vienna, maybe Germany. Somewhere around there, anyway.
Of course, like pizza, they’ve been, um, refined pretty much beyond recognition – into the plastic-cased tissue-extrusions we love so well.
Or have I been hit with the notorious reversing woosh? ::
The only truly Canadian food would be bannock and raw fish, I don’t eat either.
There’s the poverty issue (someone glanced it with mentioning African-Americans and Hispanics, two groups of people who, in the US, are poor out of their proportion).
Poor people can eat a lot in the US, but not always well. The diets available are high in fat, corn syrup and other cheap filler. Levels of poverty and wages are, on the whole, worse in the US than the rest of the Anglophone world. In a lot of poor neighborhoods there’s a push to get decent supermarkets with fresh food in where right now you have a lot of processed junk foods.
Really? Isn’t the US the world’s wealthiest nation?
There’s peameal bacon (“Canadian bacon” in the U.S.), and baked beans with MAPLE SYRUP forchrissakes!
The average wealth of a US citizen is probably quite high, but that’s because of folks like Bill Gates and Larry Ellison. If you look at other measures that are less sensitive to the skewed distribution of wealth, we don’t come out looking all that hot.
Re: Canadian cuisine:
Another food that seems to be unknown in the US but is widely popular in Canada is known as a “Hot Hamburger.” It’s a grilled or fried beef patty or two, on bread, with gravy. Usually served with fries or other potatoes, and a vegetable. Can’t get that down here, that’s for sure.
When my mother drove down here to Florida one year, she stopped at a restaurant, and asked for a hot hamburger. They’d never heard of one. So she explained it to the waitress. What came back was a burger, on a bun, with onions and lettuce and mustard etc., smothered in watery gravy. She had to send it back - it was inedible.
I’m not sure how widely popular this is: I’ve never, ever heard of this. What part of Canada is your mother from?
I’ll agree with the notion that Canadian cuisine is essentially “American food, but less of it”. We’re quite the innovaters when it comes to deserts but main courses are essentially the same. I think there’s less of an emphasis on fried food though.
She was from Southern Ontario. When I last lived there, you could get them at just about any sit-down restaurant Not everywhere, of course, but in lots of places. I also got one when I was in Vancouver. It may be regional. For instance, you could get french fries and gravy everywhere when I was a kid, but I never heard of, or tasted poutine until the 1980s. It must have migrated with some Quebecois.
cite please?
BTW, what about the Bronfmans, Belzbergs, etc.?
I’ve never heard of a hot hamburger, either. But you could always get poutine at Burger King since I can remember. Of course, BK poutine pales in comparison to real Quebec poutine. St-Hubert makes a good poutine, so does Ashton’s.