I respect Dr. Deb Bennett in her research, but another article I've read by her also states that horses should ideally not be started under saddle until they're 7 years old.
I am currently around 300lbs (I had lost a bunch of weight last spring but thanks to a change in medications for some mental problems, along with losing my job, most of it is back, my highest has been 317, so I am not there and am working my way back down now, or at least trying.
I've struggled with my weight my entire life, and when you ride horses, it seems (at least in my own experience) to lead some self-loathing. When I see come onto forums such as these just to be rude...
Anyway, I've had my mare for 12 and a half years, she is about 15.3 and about 1200 lbs, I've ridden her at all weights between 210 and 317. I haven't ridden her lately, not because of my weight gain, but because we moved barns twice this month (long story) and two barns ago I believe somebody fed her my entire ration of 50lbs of oats because I put it in my bin the night before, it was gone the day we left, nowhere in sight, and she was colicy and has been feeling icky since and I'm treating her for ulcers. At any rate, I have never had to treat her for anything beyond what horses who have lighter riders who do the same sports I've done (eventing, jumpers, dressage, and right now just trail riding cause new barn has 30+acres of private trails and I can't WAIT to explore).
My gelding I have ridden only once since last April. I had him leased, and when he came back he was sore. I finally was able to get his chiropractor out and it turned out to be his pelvis was stuck in extension, most likely from a pasture accident 6-12 months ago. Poor buddy! Anyway she said "you should try some cattle work with him" and I was like "oh, because western saddles distribute weight better?" and she looked at me like I was crazy and said "no, because it's so much fun and he's such a cool horse" and she said I was crazy not to ride him that I'm very mindful of saddle fit, riding, everything else. I haven't yet, but I will.
I'm recovering from a concussion (not horse related, you think my 1200lb horses can do damage, my 40lb blue heeler x ran into me this week and sprained my knee and pushed me down so I knocked myself out on my parent's bed frame). I am doing a lot of in-hand work, and it's fun too, but I can't wait to get back in the saddle.
My goal is to not be a 300lb sack o' taters, I take lessons and have a good trainer who helps me a lot. Sometimes I fall back into my old habits (my mare is hot and I get bracy at shows and so does she) but we can have nice, soft rides too :) My trainer's daughter (who is like a sister to me, they both are) loves to ride my mare too, she is good with hot horses because she grew up on the back of her mom's OTTB.