Fair standards for weightloss bet?

I'm a firefighter and a group of us at the station are in for a friendly wager, 8-week/16-week "weight loss" challenge (weigh in at the half and at the end).

I'm up against three guys that are pretty big and kinda chubby--I'm the lightest and the leanest of the four. So, how is the best and fairest way to measure "weight loss"???

I proposed 2 factors: 1) weight loss as a percentage of overall body weight; and 2) loss of body fat percentage by use of calipers. each factor weighed equally. I even proposed an "overall appearance" factor but there was no way to objectively measure this.

any other thoughts? anyone ever hold a challenge like this before? I wanna win!!

loss of body fat percentage would be the most accurate way to figure it out. Weight probably isn't as important for you as it is for them, because your leaner, so you'll probably just get more lean.