Just like you can weigh over the limit you can not weigh under....If you were to have a bout at HW and weighed in at 170 it would be dangerous and a liability for such a size difference.....Of course with the exception of HW...Once guys get that big it would be impossible to have weight restrictions and then expect to make fights.....

But if a guy is to fight at 147 WW lets say...at weigh in's he is not to be over the 147 limit or under the 141lb mark at weigh in time