Domino's Pizza manager T.J. Djigue creates a hand tossed pizza in Bethesda, MD. The FDA is crafting regulations that would require major chain restaurants to label calorie counts on their menus. (Katherine Frey/THE WASHINGTON POST)

A Big Mac is a Big Mac.

But a pizza? There are 34 million ways to customize it, depending on toppings and crust and size, according to the number-crunchers at Domino’s.

That’s the message that some of the nation’s largest pizza chains want to impress upon Capitol Hill lawmakers Wednesday as they push for changes to a proposed menu labeling plan that would force chain restaurants and other food outlets to post the calorie counts of the foods they’re selling.

A fledgling coalition of pizza chains — including Domino’s, Papa John’s, Little Caesars, Godfather’s Pizza and Pizza Hut — argues that the government’s plan forces store owners to pay for in-store menu boards that most of their customers don’t see before ordering. The American Pizza Community, as the coalition is called, says 90 percent of their orders are placed online and over the phone.

Then there’s the problem of squeezing all the potential offerings onto one menu board.

“A light bulb goes on when people hear about all the possible combinations for pizza,” said Lynn Liddle, a Domino’s executive and chair of the coalition. “They start to realize how difficult it would be to take a one-size-fits-all approach.”

Congress required menu labeling as part of the health-care reform law enacted in 2010, and the FDA has been working on the details ever since. The goal is to combat obesity by helping consumers make informed choices when they eat out, especially now that a third of the calories Americans consume come from foods prepared outside the home. Many studies show that calorie intake is higher when people dine out.

Under the FDA’s proposal, food chains with at least 20 locations — including sit-down restaurants, fast-food outlets, bakeries, coffee shops, delis and convenience stores — must disclose calories on menus and menu boards. Sodium, fat content and other nutritional information would have to be made available upon request.

Although this kind of information is disclosed on labels of packaged foods, it is not widely available in restaurants and other food outlets except in scattered localities (such as New York City) and a few states, including California.

The American Pizza Community, created in January, says the rules as written are unfair.

For starters, the FDA would require that a menu board display the calorie count for the entire pizza even though the average consumer eats only 2.1 slices, the group said.

The proposal also calls for posting a calorie range for foods that can be customized. But such ranges can be so wide for pizza that they’re useless, the pizza makers said. It makes more sense for customers to use online tools, such as Domino’s Cal-O-Meter, which enables people to plug in what they’re eating and get the calorie count.

Since proposing the changes in April 2011, the FDA has remained silent on the issue. This week, through a spokesman, the agency said it is continuing to work on the rule.

Mary Lyne Carraway, owner of nearly five dozen Domino’s stores in the Washington area, said the proposal would require new menu boards at each location at $3,000 to $5,000 a pop — and she’d probably end up replacing them once a year.

But Carraway predicts the changes won’t have the intended effect on consumer eating habits. She cites her 10 stores in Montgomery County, which has a menu-labeling law similar to the FDA’s proposal, as a case in point.

“I don’t see pizza counts dropping, and I don’t see salads running out the door,” Carraway said.

Although research is inconclusive on whether calorie listings influence buying decisions, health advocates say two large studies focused on New York City show that they do.

In 2009, researchers at the Stanford University School of Business analyzed purchases at more than 200 Starbucks stores in the city and found that calorie postings led to a 6 percent reduction in calories per transaction. Most of the drop was tied to customer food purchases, with little effect on drink purchaes.

New York City, which adopted menu labeling in 2008, did its own study of purchases at about 170 of the city’s top fast food chains and found that one in six customers used the calorie information. Those who did bought about 100 fewer calories than customers who did not see or use it.

Margo Wootan, a director at the Center for Science in the Public Interest, said the FDA’s proposal offers a reasoned approach to tackling the menu labeling issue.

Under the plan, the pizza chains would only need to list calories for the items they choose to present on their menu boards — not every possible pizza combination.

There’s also good reason to list the calorie count for a food item in its entirety, instead of per serving, Wootan said. That approach enables consumers to more easily compare different types of food items — such as nachos or chicken wings on an appetizer menu — and leaves it up to the individual to determine portion size.

None of the issues the pizza makers are raising are new or unique to their business, Wootan said.

“We heard the same types of arguments from the whole restaurant industry when they were opposing menu labeling in the early days,” Wootan said. “I don’t know what’s up with the pizza industry.”