I am 5' 6" and certainly very fluffy and that is being kind. LOL 7 years ago I was wearing a size 10 or 12 and that is in my dreams. I am working on losing weight and had lost 17 lbs earlier this year and then gained it back
LOL working on it again and hoping that I keep on track.
No one has ever said squat about my weight except me and I gripe enough for everyone!
I used to be a skinny minny and was a good rider years ago - fast forward to overweight was bucked off and scared rider that started over at 50. My first gelding was 15.3 former race horse and he was more than capable of carrying me. I have seen loads of big ol' cowboys that were not only big tall men they were riding small horses! Biscuit was a little under weight when I got him but he didn't seem to ever have a problem carrying me up and down hills. He has put on considerable weight - and is rode on a regular basis and has built up loads of muscles. He hasn't put a wrong step since I bought him.
I have improved in balance and my seat is pretty darn good now. I don't flop around on my horse. Do I wish I was smaller? Of course I do and have made a conscious effort to do so. I really want to do LD and 50 milers and it will certainly be easier on me and my horse if I lose 50 myself!
Horses are pretty darn tough animals - and generally will let you know if it is too much, too many, and you're not little!!! (my son used to say when he was a tot "it's too much, it's too many, I'm too little" with his little hands waving back and forth when asked to pick up his toys!)