Lawyers are gathering in Boston on Friday for the first major conference on ways of suing the fast food industry.
Controversial US research says burgers and fries are addictive
A leading participant has sent a letter to major fast food outlets urging them to display notices warning people of the allegedly addictive nature of their food.
The event comes as the US Congress debates a bill that would protect restaurants from obese people who blame fast food for their weight.
More than three in five Americans are overweight and nearly one in three are obese - with 100,000 obesity-related deaths a year.
Blaming the industry is big money
Director, US Center for Consumer Freedom
The country spends an estimated $100bn a year treating weight-related health problems.
In January, researchers in the United States said they had found evidence to suggest people could become overly dependent on the sugar and fat in fast food.
The research is highly controversial but it is likely to be used in coming court cases in the US, the BBC's New York correspondent Jane Standley says.
John Banzhaf, a US lawyer known for his campaign against the tobacco industry, says he wants the six major fast food companies he has written to - including McDonald's and Kentucky Fried Chicken - to be aware of the research.
The Boston conference will discuss strategies of suing and ways of forcing fast food companies out of schools, where they often have vending machines and franchises, our correspondent says.
Already, a group of New York teenagers have sued McDonald's - but the case was thrown out in January by Judge Robert Sweet saying: "It is not the place of the law to protect them against their own excesses."
The bill before a US Congressional committee would bar overweight plaintiffs from seeking compensation from food manufacturers or restaurants.
Lawyers are, in part, being blamed for seeking to boost their profits with such cases.
"Blaming the industry is big money," said Richard Berman, executive director of the Center for Consumer Freedom.