Usage of any of them and anything

I feel like we can use either 'any of them' or 'anyone' (anything) for the same meaning in the same situation.

For example,
There is a lot of food in front of me and I say, "You can eat any of them!" Or "You can eat anything!"

Or is there a meaning difference or a different usage of them? Thank you so much as usual for your time and help, and I do not take them for granted at all. Thank you so much again.