Firstly I must mention that there are a lot of experienced keepers here that won't use mealworms, because they can pose digestive problems to chams. The have a much higher chitin-to-meat ratio than a lot of other insects, which is what makes them hard to digest, and could even lead to impaction.
They also are relatively high in fat, so they are not good as staple feeders at all.
That said, my male cham really seems to love them, so I've always kept a batch going to feed off as an occassional treat. But I would only feed them to a healthy, adult cham whose digestive system should be able to cope well with them, and I try to feed off only recently molted worms.
I learned how to gut load superworms here and I was thinking about my mealworms. I'm sure its the same recipe but I keep them in the refrigerator. I'm imaging they don't eat when chilled.
Mealworms are usually kept in an edible substrate (like rolled oats), so that often forms part of the gutload. You can enrich the substrate by using a blend of various cereals and milk powder and other dry ingredients (like spirulina powder), but you should also be providing some leafy greens and fresh vegetables. They don't go through greens and veg as fast as crickets do, so make sure that you change the veg regularly before it goes off, and don't let it wet the substrate too much or else it will go mouldy.
Also, you're correct: the mealworms won't eat when they are refrigerated. So if you are going to keep them chilled, make sure to take them out of the fridge a few days before you feed them off so they can start eating that gutload.
Is it safe to keep them outside the fridge?
There's nothing unsafe about it, but when they are not refrigerated they will continue to eat and grow, and will eventually complete their life-cycle. That is, they'll pupate and turn into darkling beetles. You can then breed them and start the whole process over again. They will breed and lay eggs in the same container and substrate they normally live in, so the process can almost be perpetual.
