They're both champions actually, and it's more common for a fighter to go up than come down. Like say in boxing, the most powerful boxer in the entire sport right now, Mayweather, who'd been an undefeated world champ for almost two decades and the biggest star and earner in boxing, moved from welterweight to super welterweight to make the fight against Canelo. For Canelo to come down to welterweight would've been ridiculous and it'd never have happened.

A catchweight fight could be reasonably expected in this situation, but coming down an entire division is very, very uncommon. The weird thing is that MMA doesn't seem to have a division in between theirs. For example in boxing you have lightweight which is 135, then you have super lightweight at 140, and then welterweight at 147. But Ronda fights at 135, and Cyborg fights at 145, there's no 140 in between. A catchweight fight at 140 makes a lot of sense, I think, coming down 10 pounds is crazy. Going up 10 pounds is also a lot, although we mustn't forget Ronda competed in the olympics (a much tougher competition in the sport she dedicated a much bigger part of her life to) at 154 pounds, so this notion 145 is suddenly too much, and that Cyborg just has to come down to 135 is pretty silly but whatever. It's not uncommon to compete at a lower weight than the olympics, but 20 pounds is a gigantic difference and it says she could easily go 10 pounds back up. And for a catchweight bout it'd only have to be 5. If that doesn't happen I think it's clear who doesn't want to take the fight. (Ronda)

Ronda's argument counter-argument is that if Cyborg was not on steroids, she could make 135 easily. Cyborg has mentioned multiple times she can make the weight cut, yet it has not made it happen.

Steroid weight gain (for professional fighters) is mostly water weight which is relatively easy to shed for the weigh in (I referenced Canelo just now, he routinely sheds 15-20 pounds and regains it within the span of 24 hours for his fights, because it's all water weight, he doesn't have to lose fat or muscle to do so). Beyond that steroids simply help you recover better and build muscle easier, but you still need to put in the work, and you can't get bigger on a caloric deficit no matter how many steroids you use. So steroids for fighters aren't commonly associated with weight issues (they do outside of fighting, for hormone treatments or bodybuilders).

Beyond that I don't know if Cyborg's on steroids, I don't follow her much and I wouldn't be surprised if she was, but I don't see her weight as being remotely related. Again, it's extremely untypical to go down in weight classes, if that was supposedly indicative of steroids I can literally name a hundred fighters who'd be suspicious from the top of my head.

Anyway yeah she said it a couple times that she could do 135, yet it hasn't happened because she wants the fight at 140 at a catchweight I suggested (I'm just reading this now). I mean Cyborg just a few years ago won gold medals at at 74kg or 163 pounds. Now she has to drop down to 135 pounds from there, or 10 pounds from her 145 fights this year? Instead of Ronda agreeing to go up 5 pounds to 140, when Ronda competed just fine in tougher competitions at 154 before? So supposedly she's got the self confidence to fight anyone, to beat men, to even beat elite female boxers like Laila Ali IN BOXING, when Laila competed up to 175 (I mean it's just a total joke), yet Ronda doesn't want to go up 5 pounds for Cyborg to go down 5 pounds and make the fight happen?

Cyborg has been suspended in the past for steroids usage. Steroids are directly related to muscle gain and that's Ronda's point:

http://www.sbnation.com/2015/8/2/9086623/ronda-rousey-challe...

Or if you're BJ Penn, you do indeed go up a weight class to fight the (overwhelmingly dominant) champion, and win!

https://en.wikipedia.org/wiki/B.J._Penn

Both Rousey and Cyborg are champions, of bantamweight and featherweight respectively. There is no rule that one must go down in weight classes; Pacquiao, for example, went up.

Cris Cyborg is not the featherweight champion of the UFC because there is no featherweight division in the UFC. Rousey fights in the UFC. If Cyborg wants to fight Rousey, she has to come down in weight, leave Invicta and join the UFC.

Am I wrong in believing that she became the champion after beating Carano? It sounds like there are more details to MMA leagues than I'm aware of.

Correct. She beat Carano and eventually the league (Strikeforce) went out of business and got bought by the UFC. The UFC absorbed all fighter contracts. There is no 145 womens division so she had to cut to 135 or leave. She decided to leave. Now she is the 145 champion of Invicta (an all womens league) that is basically owned by the UFC now as well.

If shes smart and wants a massive payday she will cut to 135 for the Rousey fight.

Err...no. You don't actually. The reality of MMA and boxing is that you go up or down if the risk reward makes sense and you can physically handle the weight change.