How do you avoid that low energy slump in the afternoon?

I take a 20 minute nap.

For natural energy the whole day: spend 30 minutes right after waking up not using your phone at all. Go outside or look out the window for a few minutes, and walking during this is a bonus. Wait 60 to 90 minutes after waking up before any coffee. Drink a whole lot of water over the day, including at least a cup in the morning before coffee. Walk around for 10 minutes or so after lunch. And go to bed around the same time every evening.

I had this really bad and kept blaming heavy lunches. I saw a nutritionist, and he said it was a low protein, high carb breakfast doing it. Think a bagel and a banana. I got more protein in at breakfast and it really helped.

Humans aren't meant to sit at a desk for 8 hours, if I'm assuming right. Let yourself rest, really. No chat notifications or quick peeks at email. It could be a walk, a nap or just zoning out.

Don't try to avoid it, it's natural. Just know you'll get that second wind soon.

I totally got rid of it by pulling back my caffeine to two teas max, having a smaller lunch, and choosing slow release carbs and protein, like rice, chicken and vegetables.

Your post reminded me how much things have changed. My afternoon slumps used to be so bad I'd be falling asleep. Now my energy is pretty level through the day until about 8pm.

Coffee.