As (a non-religious) someone who tried fasting while holding down a similar job, my advice is simple: don't break your fast every night. It only takes 24-48 hours for your body to adjust, your fat to start melting and your blood-sugar levels to stabilise. You also stop feeling hungry. I found that while I was generally a little 'light-headed' my powers of concentration were fine and I returned to full productivity. A…
I don't think humans would become too weak to throw spears because they didn't have their Cheerios in the morning.
When I hear people who have skipped a meal complain "my blood sugar is low", I worry for their health. We have fat stores for a reason. Skipping a meal should not be a big deal.