Based on my own experiences, I'd actually expect performance to improve since the body isn't using resources for digestion. I'm not a weight lifter, but I know bicycling is significantly harder shortly after eating and my other current sport, freediving, is much, much easier after fasting (my static hold time is close to 2 minutes longer when I haven't eaten in the past ~12 hours).

One interesting observation I've had from freediving is that some of the signals we get from our bodies are far less urgent than we tend to experience them. The main one, in that sport, is the urge to breathe and it's actually not an indication that the body needs oxygen. It is, instead, an indication that CO2 is building up and you can expell it by breathing. Freedivers learn to experience that sensation and push past it.

I'd imagine hunger is very similar. People accustomed to eating whenever they're hungry will panic an experience "low blood sugar" when they don't immediately respond. But we know that humans can go weeks without eating before we die. Pushing past our accustomed non-resistence to hunger will likely be uncomfortable, at first, and then become normal with practice.