How do I change my goal on the Wii Fit Plus?
This is actually a common question. Apparently, although there's no manual option to change your goals mid-way, there is a way to "trick" the game into allowing you to change it. You can take a new test, and hold something in your hand that makes you weigh more than your goal. If you went for losing more weight, then perhaps use a pet, or a person who weighs less. That way you can "reach" your goal and set a new one.
Then you can set the new goal to lose the amount of weight you were holding for the test you just did. Then do another test without the extra weight and you'll reach your goal again, and then you can reset the goal to what you really want.
It's a flaw in the game to not be able to do it conveniently which is a shame (thankfully I've never personally had this problem). Anyway, give it a shot and see what happens. I heard there's another way too: If you play the game but it senses you're not making any progress towards your two-week mark, then it might give you an opportunity to change your goal halfway through.
Long story short: It's a tedious process but it is possible. I hope I explained this okay.