Most of the attention surrounding weigh-ins is centered on fighters beating the maximum weight limit, so it is quite easy to forget that there is also a minimum weight limit.
A fighter failing to make the minimum weight is so rare that this has to be a hypothetical situation that can only possibly take place in the heavier divisions.
According to the rules, a fighter who misses weight, regardless of whether overweight or underweight.
Ideally, a fighter who fails to meet the maximum weight limit is too big to fight in that division. One who fails to meet the minimum limit is too small to fight at that division.
The only UFC division without a minimum limit is the flyweight division, which happens to be the smallest weight class.
To fight in any other division, a fighter must be heavier than the minimum limit weight.
So if a fighter comes in underweight, they will be given the customary 1-2 hours to bulk up and try to make the limit.
If they cannot, then in all likelihood the fight will be called off.
In the UFC, there’s never been a case of a fighter being unable to make the minimum limit.
Most fighters hang around the maximum weight limit, so it is highly improbable for a fighter to be underweight in the division they fight in.
A fighter who is unable to make the minimum weight limit for light-heavyweight(186lbs) will be facing an opponent who weighs at least 205 lbs.
By weighing in at 185lbs, they are a middleweight and will not be allowed to fight at light-heavyweight.
In the present day, we have fighters weighing above the weight limit of fight night, and the smaller guy will risk being far smaller than their opponent in the octagon.
It is for the safety of the underweight fighter that the bout won’t be sanctioned.
Middleweight champion Israel Adesanya moved up to challenge Jan Blachowicz for the light-heavyweight title.
He was required to weigh more than the 185lbs mark which is the maximum weight for his division to be eligible for the title fight.
He weighed in at 200.2 lbs, and though Blachowicz weighed in at 205lbs, he admitted to being 220lbs in the octagon that night.
This size difference was evident as he easily smothered Adesanya who had previously been excellent and undefeated at middleweight.
Fighters move up and down divisions all the time.
However, only a handful have been able to win belts in two divisions.
Some of them are Conor Mcgregor, Georges St-Pierre, Daniel Cormier, Amanda Nunes, Randy Couture, Bj Penn, and Henry Cejudo.