Instructions
Click the "Wii" button in the lower-left corner of the Wii channel load screen.
Click the "Data Management" icon on the left-hand side of the screen.
Press the "Save Data" icon on the left of the screen.
Press the "Wii" icon on the left of the screen. This will bring up a screen full of small pictures representing data for every saved game file on that Wii.
Press the "Wii Fit" icon representing your "Wii Fit" save data.
Click "Copy" to copy the save file to an SD card. If you choose not to backup the file on a SD card at this time, it will be permanently lost.
Click "Erase" and press "Yes" to confirm. All "Wii Fit" data will be deleted, and the game will be reset.