UFC 2009 Undisputed

Fans are gained by winning matches. You should unlock this while going for the "Red Belt" achievement. Fans are lost by losing matches, however, there is not a set amount to be lost per match. It depends upon your performance. So if your going to lose a match, attempt to fight your best so your points and fans don't take as bad a beating as you did. If the match is close enough, you even sometimes are able to gain fans from losing matches. It all depends on the effort you put into the fights.