I use the same hay nets as
@Kelly for my mini. He is on alfalfa and gets anywhere from 1/4 to 1/2 a flake @ each feeding, depending on whether he is turned out or stalled. I have never had any issues on the alfalfa.
My Haflinger, however, is a big boy and fattens up fast on coastal. He was exhibiting classic signs of IR, so I had his blood pulled. His insulin levels were fine, but my vet advised we continue to monitor him as a horse with a high probability to progress to full-on IR.
I, myself, am insulin resistant and on metformin to treat. I know from my own diet challenges that high carbs / empty carbs aren’t good, so I moved my gelding to alfalfa too. It’s high protein and extremely low NSC.
He also gets it in a haybag for slow feeding and has done awesome on it, already losing his puppy tummy. There is also the added benefit of hoof wall improvement since the hoof wall is mostly protein.
Good luck!