Massachusetts is expected to unveil the toughest restaurant menu labeling rules in the United States on Wednesday, requiring fast-food chains to list how many calories are in the food they sell in a bid to combat obesity.

The state's Public Health Council is expected to vote on Wednesday on regulations making fast-food chains list the calorie counts of their food on their menus or menu boards.

The regulations are expected to be more comprehensive than those in California, which in September became the first U.S. state with menu labeling rules for fast-food restaurant chains such as McDonald's Corp and Yum Brands' KFC.

The action comes at a time of rising obesity in the state and in the United States, and the regulations are intended to allow people to make better-informed decisions about the food they eat.

More than half of the adults in Massachusetts are overweight or obese, according to a 2008 state report that also showed adult obesity more than doubling in 20 years. About 33 percent of Americans are overweight, while more than 34 percent are obese, according to U.S. government figures.

A restaurant calorie information rule took effect in New York City last year, and more than a dozen states are considering similar provisions.

Unlike California, the Massachusetts regulations will cover items at restaurant drive-through windows, where about 65 percent of fast food is purchased, said Judy Grant of the healthy food advocacy group ValueTheMeal.org, citing the most recent draft of the rules.

Massachusetts also will not override regulations in municipalities that impose even stricter labeling rules at fast-food restaurants, she added. In California, for example, menu labeling rules passed in San Francisco, Santa Clara and San Mateo counties were nullified by the state law.

The rising obesity rate is "obviously important when you have a state that has created such success around healthcare reform," Massachusetts Department of Public Health spokesman Tom Lyons said.

In 2006, Massachusetts passed a law that requires virtually everyone to have health insurance or face tax penalties. For those earning less than the federal poverty level of $9,800 a year, coverage is free.

Some restaurant companies have objected to additional government regulations. In New York City, for example, some have fought the menu labeling rules with lawsuits.

Some chains instead support proposed legislation in the U.S. Congress known as the "Lean Act" that would require restaurants and grocery stores that serve prepared food to post calories on menus, menu boards or other similar ways.

Critics of that legislation say it would merely tuck calorie information at the back of menus or in a separate brochure. They say consumers need to know the nutritional value of meals because more people than ever are dining out.

"There was some sense that we should model it on the very large restaurant markets of California and New York City," Lyons said. "Many of the companies we will cover as part of the regulation will have already had to comply in those markets."