The idea that such fast-food restaurants such as McDonald's and Burger King are to blame for obesity is being challenged by a new study released by the United States Chamber of Commerce.

"Lawyers hungry for more money should resist the temptation to take a bite out of the fast-food industry," Lisa A. Rickard, president of the Chamber Institute for Legal Reform, said in a news release.

"Overweight Americans will not find the solution to obesity in the courtroom but in making wise choices to eat smaller portions and healthier foods wherever they go," she added.

The study acknowledges that over half of Americans are overweight, but links the problem to a lack of exercise and a change in eating patterns.

Burgers, Fries and Lawyers: The Beef Behind Obesity Lawsuit says that Americans have become more sedentary, snack more frequently, and consume 200 calories more each day than they did in the 1970s.

"Fast food restaurants are not a chief culprit in the fattening of America. But let us be frank here. Depending on what you pile on it, a fast food burger may not enhance your health ... but it is very easy to find out how fatty that burger is," the study says.

Former White House economist Todd G. Buchholz authored the report. He speculates that tort lawyers across the United States are zeroing in on the fast-food industry after a $246 billion tobacco case was settled several years ago.

He says there are significant differences between the fast-food and tobacco industries. He argues that "no one, so far, has shown that cheeseburgers are chemically addictive."

The study also dismisses suggestions that the fast-food industry engages in deceptive marketing practices.

Buchholz says that fast-food chains willingly and readily provide nutritional information about their products.

"You do not need a tort lawyer by your side to pry open a brochure or to check the thousands of websites that will provide nutrition data [on fast food]," Buchholz said.

A 2003 consumer trend report by Millward Brown Goldfarb found that most Canadians believe personal choices related to diet and exercise have the biggest impact on an individual's weight.

The respondents blamed sedentary behaviour (59 per cent) and the popularity of fast food (48 per cent) as the dominating factors behind rising obesity in children.

According to the report, most Canadians believe food manufacturers should develop healthier alternatives in their product lines. At least one major food company is trying to move in that direction.

Kraft Food, which creates such products as Oreo cookies, says it's changing its recipes and reducing portion sizes to help fight obesity.

"We're making these commitments first and foremost because we think it's the right thing to do," Kraft spokesman Michael Mudd said. "If it also discourages a plaintiff's attorney or unfair legislation, that's just fine with us."

Some analysts see the move as a defence against lawsuits. Earlier this year, a California lawyer has tried to have Oreos banned because they are made with artery-clogging trans fat.