WASHINGTON (CNN) - Eating smaller portions and healthier foods will do more to counter the spread of obesity than "McLawsuits" aimed at the fast-food industry, a leading business group said Wednesday.

"Fortunately or unfortunately, Americans' freedom of choice includes the freedom to overeat," said Lisa Rickard, president of the U.S. Chamber of Commerce's Institute for Legal Reform.

Rickard said the chamber has thrown its support behind a bill that would exempt the food industry from lawsuits such as those filed against McDonald's and other companies. She said plaintiffs' lawyers and public health advocates "have fixed their legal assault weapons" on fast food.

"Even if fast-food critics are well-meaning in their intentions, they are trying to fix a very legitimate problem, obesity, through illegitimate means," Rickard said. "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."

McDonald's faces a lawsuit from public health advocates who argue its food is misleadingly advertised as healthy. Lawyers for McDonald's say the lawsuit is based on incomplete information and outdated material.

Kraft Foods, which was sued over the fat content of its Oreo cookies, announced it is taking steps to fight obesity by reducing portion sizes of some products, eliminating in-school marketing of its brands and reducing the fat content of various products.

The ultimate result of such lawsuits "is to rob people of their choice," said Todd Buchholz, a former White House economist who conducted a study of fast food for the chamber.

While the study does not deny that obesity rates are increasing, Buchholz said fat levels in fast food and home-cooked meals have declined since the 1970s.

He said the increasingly sedentary lifestyle of many Americans has contributed to increasing obesity. And unlike lawsuits against the tobacco industry, no one has ever argued that fast food is addictive, he said.

"I've never seen anyone standing outside of a Wendy's shaking from withdrawal symptoms," he said. "No one has ever claimed they became fat because of second-hand eating."

The chamber came out in support of a bill sponsored by Rep. Ric Keller, R-Fla., that would bar lawsuits against food companies whose products are in compliance with existing laws and regulations. The measure, dubbed the "Personal Responsibility in Food Consumption Act," is currently before the House Judiciary Committee.

"Obesity is a very serious problem," Rickard said. "It's not going to be solved in the courtroom."