Wii Fit U has suffered a delay in Europe and will now release December 13. The game was originally scheduled to hit retail on December 6.
We regret to announce that #WiiFitU will now launch in retail outlets on 13/12, 1 week later than the original date of 6/12
— Nintendo of Europe (@NintendoEurope) November 12, 2013
Wii Fit U is currently available as a free trial download from the Nintendo eShop, but you will need a Wii Fit Balance Board to play it. The trial will last 31 days from the first time it is booted up and is available until January 31, 2014.
If you wish to keep playing after the trial expires you will have to purchase a Fit Meter and then sync it to your trial copy of Wii Fit U, this will unlock the game forever.