There's a new game of who's-to-blame boiling in the U.S. and spilling into Canada. Some legal minds in the world's two fattest nations are looking at who is making North Americans obese.

"I think when a fast food company deliberately doesn't tell you important information, that both legally and morally they bare some responsibility," says law professor John Banzhaf, of George Washington University.

Banzhaf has helped mastermind lawsuits against big tobacco firms who didn't tell smokers about the addictiveness of nicotine.

"That's deception by omission," says Banzhaf.

But tobacco firms aren't the only ones blowing smoke. McDonald's recently agreed to pay out $12 million for not disclosing it used beef fat in its french fries.

"Perhaps the entire food industry has a duty to let people know that these products containing very high saturated fat and a lot of cholesterol can harm them," says James Pizzirusso, a plaintiff in a case against McDonald's.

Roughly 55 per cent of Canadians say they want more information on healthy food choices. But people have to ask for such information at most fast food chains.

Restaurants don't advertise that eating a typical hamburger combo means eating all the fat you need in a whole day.

Some American lawyers say that could make for the next wave of lawsuits.

"Major food companies are vulnerable to these kinds of suits, if they misrepresent or fail to disclose certain facts about their foods," says Banzhaf.

But as long as the food is safe, the U.S. restaurant industry says, "We're not really in the role of telling them, a customer, what they can and can't eat," says Steven Grover, of the National Restaurant Association.

Recently, the U.S. Surgeon General estimated obesity costs the American economy more than $117 billion every year. That's right on the heals of smoking, at $130 billion.

Canada is leading the world in efforts to snuff out smoking through advertising. But whether french fry boxes will come with warnings of clogged arteries and heart disease in the near future remains to be seen.