Keeping Obese People Out of the Exit Aisle
 

What's the rule on huge people in the exit aisles?

It is up to the airline. In Europe most airlines operate the rule that if you require a seat belt extension you can't sit in the emergency row. In the US the airline must determine if you are capable of understanding the emergency evacuation instructions and fit and able to carry them out. It is largely down to the judgement of the FA.