Is there a best time (of day) to fast?

Based on current research in humans, there is limited consensus around optimal meal timing for people who practice intermittent fasting. We generally become more insulin resistant as the day progresses, or less able to clear blood glucose and get it to where it needs to go in our bodies. For this reason, it’s probably best to consume most of your calories earlier in the day and to start your fasting window several hours before you go to sleep.

“Your body can’t deal with nutrients (glucose) as efficiently later in the day, so you might as well give your body a break from glucose then,” Dr. Krista Varady says. “Early in the day, your body is primed and ready to deal with an influx of nutrients.”

If you are practicing an alternate day fasting regimen in which you eat under 500 calories on your fast days, you can either eat these calories in a single meal or divide them into three small meals throughout the day. Allowing for flexible meal timing on these fast days may help you maintain your fasting practice long term.