"Rampage" told Ariel Helwani on Monday's edition of The MMA Hour that he has diagnosed with an underactive thyroid, which makes him gain weight more rapidly than normal. Jackson said because of that he might never fight at 205 pounds again.
"I've been dealing with this for like a year," Jackson said. "I've been keeping it kind of to myself. It kind of bummed me out. If I don't stay on top of it, I gain weight really fast. That's what's been going on. I've been noticing after my fights I've just been gaining more weight fast, I didn't know what was going on.