[ThrustVectoring]

You've got the energy levels and eating relationship reversed. Over the short run, digestion uses a lot of energy and generally does not give super quick results. Especially if you're eating cleaner food (vs giant piles of sugar etc).

The more involved answer involves talking about the sympathetic and parasympathetic nervous systems (SNS vs PSNS). The SNS is activated when doing things like going for a run, focusing on a specific problem, fight-or-flight, and other generally short-term "do things or have issues" situations. It does large systematic things that make your body better at overcoming the short-term obstacles in your life.

The PSNS, on the other hand, is responsible for more long-term survival goals. Sleep, digestion, relaxing, general awareness, etc.

Another important fact is that activating one of the circuits tends to deactivate the other. Eating activates the PSNS. Having "high energy" and not feeling tired/lethargic is basically a high SNS activation state.

[richmt]

I'm more curious about the second question I raised. I've read stuff before saying x grams of protein can't be absorbed when consumed in one meal. I've heard differing claims, some saying it's a myth, but I would imagine it's possible.