By Jonathan Stempel

Nov 26 (Reuters) - A federal judge dealt a setback to customers suing Burger King over advertising for its Whopper sandwiches, saying their claims were too disparate to justify certifying a nationwide class action.

The lawsuit by 19 customers in 13 U.S. states accused Burger King of misleadingly and materially inflating the size of nearly all menu items online and on in-store ordering boards.

These included Whoppers whose burgers allegedly appeared to "overflow" the buns and be 35% larger than they are, with more than double the meat.

But in a decision on Tuesday, U.S. District Judge Roy Altman in Miami said the state consumer protection laws underlying the lawsuit had many differences. He also said individualized claims would predominate because the plaintiffs bought burgers in an "almost-infinite variety" of shapes and sizes.

"It may be that every single one of those burgers was smaller than every single menu-board item Burger King has ever produced. But that’s not the point," Altman said. "Each putative class member will have seen a particular photo and received a specific burger."

The judge also said Burger King's prices have "undoubtedly waxed and waned" since April 1, 2018, the start of the proposed class period, and all class members would need to show when and where they bought burgers, and what they paid.

Lawyers for the plaintiffs did not immediately respond to requests for comment.

Altman had rejected Burger King's bid to dismiss the case in May, but Tuesday's decision significantly reduces the potential damages.

Burger King said it was satisfied with the decision. It repeated its May statement that the plaintiffs' claims are false, and that "the flame-grilled beef patties portrayed in our advertising are the same patties used in the millions of burgers we serve to guests across the U.S."

A federal judge in Brooklyn, New York dismissed a similar lawsuit against McDonald's MCD.N and Wendy's WEN.O in September 2023.

Burger King is a unit of Restaurant Brands International QSR.TO. The Toronto-based company’s brands also include Tim Hortons, Popeyes and Firehouse Subs.

(Reporting by Jonathan Stempel in New York; Editing by Alistair Bell)

((jon.stempel@thomsonreuters.com; +1 646 223 6317; Reuters Messaging: jon.stempel.thomsonreuters.com@reuters.net/))