When Sen. Angus King shows up Thursday at a Domino’s pizza parlor in Standish, he will highlight his fight against proposed rules to specify how restaurant chains inform consumers about the number of calories in the food they buy.

The rules, passed as part of the Affordable Care Act but not yet finalized, call for nutrition labeling of “standard” menu items by chains with 20 or more restaurants, as well as convenience stores and grocery stores that sell ready-to-eat foods such as hot dogs and salads.

Many fast food chains don’t oppose the proposed federal rules because they would replace a hodge-podge of local and state rules with a standard that would be easier to manage.

Pizza chains, including Domino’s, appear to be leading the fight against the rules, which are being developed by the U.S. Food and Drug Administration. The FDA has been working to draft the rules for more than three years, but has yet to issue the final version and has already missed several deadlines in the process.

King, an independent, is a co-sponsor of a bill that would give pizza chains more flexibility in posting information about their food, and would exempt most grocery and convenience store chains. U.S. Rep. Mike Michaud, D-Maine, is a sponsor of an identical bill in the House.

Restaurateurs and grocers across Maine are already struggling with a sluggish economy and cumbersome federal regulations, King says. “Regulations play an important role in keeping people safe, but we have to ensure they are smart, targeted and effective,” he said in a prepared statement. “Otherwise, they will only stifle economic growth.”

Consumer health groups, which have long fought to make more nutritional information available, oppose efforts to treat pizza restaurants differently from other chain restaurants. Pizza is among the top five sources of caloric intake for Americans, said Marion Nestle, professor of nutrition, food studies and public health at New York University.

“The thick-crust ones with lots of cheese are staggering in the number of calories they have,” she said. “This is not trivial.”

King’s bill serves as a warning to the FDA that Congress will take action if the agency’s rules are unreasonable, said Lyle Beckwith, a lobbyist with the National Association of Convenience Stores.

“They are geared up, and they want the FDA to know they are geared up to move something if they get it wrong,” Beckwith said.

Among the chains that don’t oppose the new rules is Subway, which has made calorie counts and other nutritional information part of its marketing. The sandwich store chain offers details right down to the toppings: three slices of pepperoni is an extra 80 calories; an extra slice of American cheese is 40 calories.

According to choosemyplate.gov, a website managed by the U.S. Department of Agriculture, men who are 31 to 50 years old and aren’t physically active need 2,200 calories a day. For inactive women in the same age range, the total is 1,800 calories.

Mike Mullen, the Domino’s Pizza franchise owner who plans to host King in Standish, said the rules would pose a challenge for pizzerias, which sell a custom-made product with a nearly unlimited number of combinations.

And Mullen, a former Domino’s delivery driver who now owns three pizzerias, said his business isn’t the kind of large corporation that could afford the cost of the new labeling requirements, which he estimates would be nearly $5,000 a year.

Mary Adolf, president of the International Pizza Hut Franchise Association, questioned the effectiveness of posting nutrition labels at restaurants when most pizza customers order on the telephone or the Internet. Moreover, the preliminary rules would apply to an entire pie, rather than a slice.

“Hardly anyone can eat a whole pizza pie,” she said.

Mullen said one effective and less expensive way to deliver the same calorie information to consumers is the Domino’s Cal-O-Meter, a feature on the chain’s website that lets a customer build their own virtual pizza and watch the calories accumulate as they choose their toppings.

For example, one slice of a 14-inch pizza with triple cheese would have 390 calories, according to the Cal-O-Meter.