Just wondering. Is it even possible without actually trying to lose?

No.

Yeah, it's possible to lose. At least, I've lost, as an Altmer (twice, on two separate characters) against an Orc (that guy in Cidhna Mine). The two characters in question were a mage (no health to speak of, so not really surprising) and a thief (more stamina than health, for carrying/running purposes), but I think the racial weight differential also made a bit of a difference. I haven't really brawled with them anywhere else, though, so I don't know if wearing armor (light armor, anyway) makes any difference.

I've wondered this, also. I was trying to boost my flacid wounded ego by telling myself I never lost a brawl because of my veteran Tekken status.
But, sadly no. Seems the indignity of loosing a fight to some mere human would be too much for the mighty Dragonborn to handle.

All my characters so far have been heavily armored warriors, so i wasnt sure if it was normal to win all the time or not. Will have to give it a go with my new Bosmer.

I have not.

I have not. Of course, the only brawl I do is the one in Windhelm (Rolff Stone-Fist). I love that brawl, I get to beat up a racist and get 200 gold!

Is it cheating if you use health potions/healing spells during the brawls as a mage? (100 hp, 100 stamina, about 300 magicka)

yes, they tell you know magic or tricks, just fists. you cheater. even if he is a racist, he deserves a fair fight.

I buffed up the difficulty by 2 (cant remember the name of it)
At the time I almost lost, I was a Breton with like 100 health, but I used a potion to heal. It was my first brawl ever, and that was awesome. I wasnt sure if I'd die if I lost, so i had to heal up lol.

I only play magic characters or thieves, and I have yet to lose a brawl on any of my characters, playing on adept. I mostly play altmer,
breton, or dunmer if that makes a difference.

to really troll someone, wear the heaviest armor, and upgrade it excessivley.

I havent lost and i'm using a altmer wearing robes and didnt put any points in stamina or health..i've brawled with 3 orc clan leaders,.uthberg the ugly and several others

What happens if you lose? Do you die or just take a kneel?

I had to do a radiant quest for the Companions to fight some guy in the Windhelm Inn.

I'm playing on master, with no points in health and at that time a very low armor rating (since you can't really get hit anyway on master). Suffice to say; the guy would have kicked my shiny little hiney if it wasn't for me being allowed to start shooting arrows into the guys face halfway through the fight.

It was a bit of a desperate move on my part and I was expecting people to attack me. But the crowd in the Inn just kept on cheering while the guys face turned into a pin cushion. Still took me plenty of arrows but they got the job done in the end.

So to answer your question: No, I have never lost a brawl.

I was trying to see what I could get away with in a brawl, I brought out the torch and kept guard bashing Mikael to set the little pervert on fire, which nobody really seemed to mind. Everybody kept cheering for him though it was kind of weird, they're like "Yeah! Kill that cute tiny little Breton girl!" Good job guys, cheer for the womanizing abusive [censored].
I would like to know this as well.

I've never lost so far, having brawled with three character, Heavy Armor warrior, Light Armor warrior, Light Armor rogue. So maybe it'll be harder with a pure mage in cloth.

Even with high-health opponents, you can pretty much win with no health loss by punching and dodging, as long as you have some space to move around. Punch, move back for his swing, rinse and repeat.

no but im always annoyed at how long brawl matches last.

QFT.

yes they take 100 gold from you but, you can fight then again

No. Nord Warrior-type. ...and now that I have the Perk (Fists of Steel or Heavy Hands - armor rating bonus to damage) the fights are short.

I'd guess I've been in at least 15 brawls now (with three characters, each with different builds). None of them have lost a brawl.

I've never lost a brawl, but then I tend to have high HP and armor rating. The former came in handy against the Orc in Cidhna Mine, since I had no armor at the time, but usually I persuade my way past him instead.

As inept as the NPCs are you'd have to actually try in order to lose a brawl, although I suppose trying it at a really low level might also work.

One does not simply... LOSE in a brawl...

The Cidna Mine Orc was very close, but he was the only one. All other brawls were cake walks.

I lost once with my mage. I had to dodge a lot and didn't want to use any tricks/potions. Got stuck behind a table and went down. You just take a kneel. I won the second time, but it can get hard as a pure mage.