Best way to track weight lost results in competition?

My fraternity wants to do a weight challenge. We have 9 people who want to participate. We want to do teams of 3 to do competition style. Im having a hard time figuring out how to match the teams since we have a wide variety of body types. Can any one help me figure how to arrange the teams so its fair and decide whats the best way to track results for each in a fair manner. Also how to figure each thing such as BIM or body fat.