Similar age, noticing the same. It never used to matter. Although I also used to have jobs where I was on my feet all day so I’m not sure what is aging and what is living a sedentary life. I usually have a handful of almonds in the afternoon and that’s fine. Also avoiding afternoon coffee seems to help.

But I’ve started walking for a half hour before work and after a couple weeks, I feel like I have more energy in general.