Two of mine went for an absurdly long time without eating, but that was only when I first brought them home. And Desdamona's off her food at the moment, but that's because she was stressed about having salt baths every day for a while, but she'll be eating like a pig again soon, I'm sure.
Yes, red meat from animals does contain higher amounts of fat then would normally be in an axolotls diet.
I've always just waited out my axolotl's little hunger strikes, because there wasn't much else I could think of to do.