OK, now I have read it, and my take?
I need to look at the source article, not a newspaper report of the findings, because we all know you can't trust the media.
10% sounds a very very light ratio, and would remove swarths of riders from the population.
For arguments sake, lets take the 10% as new cutting edge research and the new reality is that no horse will carry more than 10%, what would be the law of unintended consequences here?
Lots and lots of riders would now be unable to ride their horses, a % of them may successfully lose weight and maintain that loss, so they will be good to go. But there are a whole bunch of us who will never be able to sustain a weight that is 10% of our current mounts so what happens to them? I presume that the purchase price of draft crosses would shoot up, but lighter horses what would be the welfare considerations there?
I am assuming that horses all suffer some sort of wear and tear damage from most anything that we do to them, be it chasing cans, cutting cows, jumping fences, being a dressage star, each discipline must have some degree of damage, it is probably a question how much we are comfortable with.