It's been just days since Nintendo Co.'s fitness video game Wii Fit was made available in the U.S. but the product is already selling out across the country.

Important online retailers such as Best Buy, Wal-mart, CircuitCity and others all over U.S. were sold out of Nintendo's innovative exercising video game early on Wednesday, the day Wii Fit was distributed all across America after making its official debut on Monday. The game sold out on Amazon weeks ago through pre-orders causing the company to be actively seeking more products from suppliers.

Available for $89.99, the package includes the Wii Fit software disc and the hefty balance board, which measures the user's body mass index before setting players on diverse workout routines. Measuring 20.5 inches by 13 inches by 3 inches, the board which is basically a complex floor-based game controller, senses the user's weight as he steps on it and uses the information to control and synchronize the onscreen games and exercises designed to improve your balance, posture and fitness.

However, according to recent numbers released by Media Create Co., Wii Fit sales in Japan, where the game sold over 2 million units since its launch in December last year, registered a minor decrease over the past week (May 12 – May 18) selling 41,572 units from 67,308 units the week prior.

Wii Fit achieved quick sales success upon its UK release late last month ranking in five positions in the top ten game sales for the week, including Mario Kart Wii at No. 2, Wii Fit at No. 5, and Famicom Wars VS at No. 6.