Gutloading is feeding your feeder insects with super-foods so their nutritious value goes up.
You can either just make sure your feeder insects get good foods or you can add a gut load formula to their food which is high in vitamins and minerals.
So the benefit is that the insects have a higher nutritious value to your cham.
As I do not breed my own crickets I don't know what their nutritious value is when I buy them so I add a gut load formula to the fruits/veggies I feed to them to give a boost to their nutritious value...
If you breed your own you may just want to give them a healthy diet...
I do this as an addition to the supplements I use to powder the crickets, not as a replacement of them.