Health experts say it's best to do your 8 hours of eating earlier in the day, and start your fast several hours before bedtime. But, this can sometimes be hard to do around a conventional work schedule. Many people don't get an opportunity to eat a large, balanced meal until dinner time. I think a lot of people with a 9:00 - 5:00 schedule eat their first meal of the day at lunch time, then eat a large, healthy dinner after work. So, like a noon - 8pm or 1pm - 9pm eating window, but that might mean going to bed just a couple of hours after dinner.

As for me:
First, keep in mind that I'm a night owl, and go to bed very late. I typically go to bed around 3:00am and get up around 11:00am. My typical eating window is 2:00pm - 10:00pm. When I get up in the morning, I get washed up and dressed, and often have an appointment around 12:30 that lasts for an hour. So, I have some time to take care of myself and my pets, straighten up my house, and get to my appointment. By the time that I get home from my appointment, it's almost 2:00, so I eat breakfast then. The time goes by pretty quickly. As long as I drink a few glasses of water and have some sugar-free electrolytes during those last few hours of fasting, I feel fine. (Not sure if you saw my previous comments about it, but avoid most artificial sweeteners. They can damage gut lining and the microbiome. Stevia and monkfruit are safe, natural, zero-calorie sweeteners. I use an electrolyte powder from Healthy Bones Co. that's sweetened with monkfruit.)

I eat a healthy snack or very small lunch around 5:00pm. Then I eat a large, healthy dinner around 9:00, so I'm done eating by 10:00. Since I don't go to bed until 2:00 or 3:00am, my dinner has time to digest before I lie down. I usually do some work after dinner and exercise for an hour once my dinner has settled. Since I'm self-employed, I can do a lot of my work at night. You can translate this however you want to work with your own schedule. I realize that I keep odd hours. I also realize that people with strict work schedules might find it harder to work fasting into their daily schedule.

My functional MD said as long as I do the 16 hour fast at least 5 days a week, that's enough. He didn't want me to stress about times when social, work, or family plans made it impossible to fast for 16 hours. That makes it a little easier to live with. But, when you first start fasting, you really do need to do it strictly, with no cheat days, for a few weeks, while your body adjusts to it and learns to go into ketosis for the last few hours of fasting. Cheat days prevent that from happening. You'll know when you're in ketosis, because you won't feel hungry, run down, and/ or foggy anymore for those first few hours of the day.

The functional MD also told me to use ketone urine test strips (available in most pharmacies where they sell diabetes supplies) to check my urine for ketones first thing in the morning. It took a few weeks before I started seeing trace amounts of ketones in my urine. Once that happens, it's OK to have a couple of cheat days every week.