I feel like there's something wrong with that. 168pounds at 5'7" gives you a 26.3 BMI rating which right in the overweight range (starts at 25). There's nothing wrong with that. BMI also doesn't factor in if you've got a lot of muscle.

However, losing 8 pounds in two weeks is possible.

Also, there's all kinds of numbers about rotating mass and non-rotating mass. Losing weight off something rotating (cranks, wheels, pedals) does help more than non-rotating mass, but the question is how much? In my opinion, it doesn't make that big of a difference, but this is just from my personal experience and what I've noticed.