A thin young ( in shape) horse is way better than a fat horse standing in the pasture that knows nothing.
x2...
... back when I was riding 10-15 a day, it was nothing to pull a few hundred pounds off a colt in a short period of time... certain horses require extreme work loads to "get beyond" certain issues... no matter how much you feed them.
Communication with your trainer and regular "shows of progress" will help prevent things from getting out of control...