Sumo wrestlers were the main inspiration behind Wii Fit, Nintendo's latest attempt at getting you off the couch when you play video games.

Because they are so huge, sumo wrestlers need two scales to weigh themselves. Wii Fit's balance board works kind of like two scales fused together, which, as its designers found, makes it instantly more fun than just one. The game has sold more than 2 million copies in Japan and it's been a hit in Europe. Nintendo Co. hopes to recreate that success when Wii Fit goes on sale in the U.S. on Monday.

In the U.S., pre-launch buzz around the game _ whose activities range from yoga to snowboarding _ is reminiscent of the Wii's debut. The console, initially elusive in stores and online, is still often in short supply a year and a half after its release.

Wii Fit, which costs $89.99, is currently sold out in pre-launch sales on Amazon.com and the Web sites of retailers GameStop Corp. and Wal-Mart Stores Inc., while Best Buy Co.'s Web site lists it as "coming soon."

"Our main premise in creating Wii Fit was (to) create a game that allows you to check your weight," Shigeru Miyamoto, the legendary game designer behind Mario and Zelda, told The Associated Press through a translator during a recent visit to the U.S.

Miyamoto, 55, started checking his weight daily about five years ago, a few years after he began exercising to stay healthy. Tracking his progress, he said, was fun and his family soon caught the bug.

"We ended up buying a brand new scale, and I started thinking that if there was a way I could weigh myself in the living room and make a product out of it, that would be something everybody could relate to," Miyamoto said.

With the scale as a launching pad, Miyamoto and Wii Fit's other developers added balance-based fitness activities and games. In one, you play a penguin trying to catch fish in the air while balancing on a block of ice. Like the Wii's motion-sensitive wireless controller, Wii Fit's balance board is intuitive and takes no video game skills to master.

During play the balance board becomes a snowboard, skis or a tightrope. The game's fitness regimen includes yoga, aerobics and strength training, as well as tracking of your weight and body mass index. You can even jog without the board, holding the Wii's wireless controller in your hand. The exercises start in one- or two-minute spurts, so you don't overextend yourself, and you progress to new levels as you get more proficient.

The goal of Wii Fit, Miyamoto said, is simply to get people to think more consciously about their health.

Instead of going after core-gamers _ the "Grand Theft Auto" audience of boys and young men _ Nintendo has been roping in the whole family, including moms and grandmothers, and getting them playing (and buying) the Wii.

Wii Fit seems to be expanding the Wii's audience even more. In Japan, between 30 percent and 40 percent of people who bought Wii Fit also bought a video game system for the first time, according to Miyamoto.

Mike Hickey, an analyst with Janco Partners, said Wii Fit exemplifies how the appeal of video gaming has expanded.

"It's becoming less threatening, easier to digest," Hickey said.

The game's launch outside the holiday season may also show the industry is maturing into a form of mainstream entertainment. While game companies still make most of their money around the holidays, Hickey and other analysts expects this to change.

"There is no reason you have to be tied to the holiday months any more," he said. "Like the movie business (games are) a legitimate form of entertainment in the non-Christmas tree months."

While some in the industry have questioned how long Nintendo can keep its momentum _ after all, more causal gamers may not want to spend every spare dollar on a new video game _ analysts are upbeat.

"I don't think we even had the imagination a year ago that Wii Fit could be compared to 'Grand Theft Auto," Hickey said, referring to the popular crime game franchise, whose latest installment shattered sales records when it hit store shelves last month.

If U.S. sales compare to Japan's, Hickey said Wii Fit will likely sell about 3 million copies in its first couple of months, depending on supply constraints.

Cammie Dunaway, executive vice president of sales and marketing at Nintendo of America, said people have responded in "unprecedented numbers to retailers' pre-sales." While the game sold out online, Dunaway said Nintendo wants to ensure there is a "healthy balance" between brick and mortar stores and online pre-orders.

With its exercise components, weight and body mass index tracking (as well as gentle nudging when you don't exercise for a few days) Wii Fit can certainly sound more like a health gadget than a game. In Miyamoto's eyes, however, it's a video game.

"In my mind anything that lets you interact on a TV screen, technically speaking, is a video game," he said. "But it's true that with Wii Fit you are doing things that you typically don't do, like checking your weight."