I so rarely chime in on threads related to weight. I, like many others, could definitely stand to lose a significant amount. Would it improve my riding - probably. Would it improve my horses' quality of life - negligibly.
My personal opinions on the rider weight/horse issues are
1. The horse is my property and therefore my business;
2. As long as the horse is mature, tacked properly, vetted, healthy, reasonably fit, reasonably sound, current with farrier work, etc, then I see no reason why he can't cart around a heavy person in a *fair* situation.
Note: it is not *fair* to expect a light horse to carry a heavy person over jumps, mountains, 6+ hour rides, etc. Use some common sense;
3. The amount of work most heavy horseowners expect from their horses is far less than horses of the past were expected to do and also far less work than equids in less developed countries perform today;
4. I'm sure my horses prefer carrying my fat butt around the amount they do over carrying a skinny guy around or pulling a cart all day every day; and
5. If overweight/obese people are so awful and hurting the horses, would those horses be better off slaughtered?
I think that gets the gist of my point across.
Life is too short to waste time riding/training horses that you don't love. You are a rider! While it is nice to watch green horses reach training milestones and progress, will that enough for you for the next couple years? Wouldn't you rather reach the milestones together with a horse that has a few years of riding down already?? For instance nailing a 10 on a maneuver, reaching the next dressage level, or scoring a high percentage on an individual test.
GH - you are too kind and big-hearted. I think sometimes the opinions of random internet people get to you. Don't let them bring you down or make you feel bad or second guess yourself. Don't make your horse ownership decisions solely on weight and the opinions of anyone other than your vet, farrier, family, and/or equine experts you personally know. Keep the horses you enjoy the most.