I used to schedule my easiest tasks for 2 p.m. because I knew I would be useless. Every afternoon, right around the time I should have been productive, my eyelids got heavy and my brain felt like it was wrapped in cotton. I blamed it on not sleeping enough. I tried more coffee. The coffee made me jittery and then the crash was worse.

Turns out the afternoon slump is mostly about what you eat at lunch — and a couple of other things that are easy to fix.

It is the blood sugar spike and crash

When you eat a carb-heavy lunch — sandwich on white bread, chips, a cookie — your blood sugar spikes. Your body releases insulin to bring it down. Insulin overshoots, your blood sugar drops below baseline, and you feel tired. It is not a character flaw. It is biochemistry.

The fix is not to avoid carbs entirely. It is to pair carbs with protein and fat. A turkey sandwich on whole grain bread with avocado is fine. The same sandwich on white bread with nothing else is a ticket to nap city. The protein and fat slow down digestion so your blood sugar rises and falls gradually instead of spiking and crashing.

Portion size matters

A large meal diverts blood flow to your digestive system and away from your brain. That heavy, sluggish feeling after a big lunch is your body prioritizing digestion over thinking. Eat until you are about 80% full — satisfied but not stuffed. You can always have a small snack at 3 p.m. if you need it.

Dehydration feels like fatigue

Mild dehydration — the kind where you are not thirsty but you have not had water in a few hours — reduces blood volume and makes your heart work harder to pump oxygen to your brain. The result feels exactly like being tired. Drink a full glass of water with lunch and another one around 2 p.m. I started doing this and the difference was noticeable within two days.

Move for five minutes

After you eat, walk around for five minutes. Not a workout — just walk to the mailbox and back, or pace while on a phone call. Light movement after eating blunts the blood sugar spike by about 30%, according to several studies. It is the cheapest energy boost available.

I still get tired some afternoons. But it is occasional now — when I actually did not sleep well — instead of every single day at 2 p.m. like clockwork.