My horse is Insulin resistant, he eats triple crown low starch, a tiny amount of alfalfa and coastal hay 24/7. I let him out on pasture for about 5 hours a day. He gets rode about four times a week. This is what works for my horse. He is doing great once we found out what the problem was.
I feed Safechoice Senior and he also gets Pergolide once a day plus as much hay as he wants. He gets tested once a year for any changes, this year we had to up his dosage. It has helped him out a lot adding this to his feed.