What Is the Best Time of Day To Start a Fast?

What Is the Best Time of Day To Start a Fast?

Video | Eating at Night | Your Circadian Clock | Shift Work

To practice intermittent fasting, you need to split your day into two parts: your eating window and your fasting window. But, does it matter when you start your fast? I provide some insights on that question in this blog post.

The Best Time of Day to Start a Fast – Summary


  • Many people begin their fast after dinner and break their fast with lunch the next day
  • Additional benefits can be gained by starting your fast earlier in the evening.
  • Shift workers can benefit from a shortened eating window. The degree of benefit may depend on the quality of sleep during off hours. 

What Is the Best Time of Day To Start a Fast? [Video]

In this video, you’ll learn…

  • If it is ok to eat at night!
  • Benefits from starting your fast earlier in the day.
  • Strategies for shift workers.

Eating at Night: Yes or No

The most convenient time for most people to fast is between dinner and lunch the next day. But, what if your schedule doesn’t allow for that because you are a shift worker or you just like to eat at night? Are you wondering if you can eat at night or have a bedtime snack, and then self-correct by extending your fast longer into the next afternoon?

The authority to go to for the answer to when best to start a fast is Dr. Satchin Panda, who is a pioneer in time-restricted eating and how it is linked to our circadian rhythm. This rhythmic internal clock is what guides our rest and active periods, and encourages us to eat, sleep, and be active at different times of the day.

What we learn from Dr. Panda’s work is that simply restricting the number of hours you eat during a day, allows you to reduce your calorie intake and increase weight loss. 

One of his earlier and more famous studies, showed that when overweight individuals changed their eating window from greater than 14 hours down to 10 to 12 hours a day, they experienced a reduction in body weight, and reported being more energetic, and having better quality of sleep (1).

A particularly interestingly part of this study was that participants were not asked to change the quality of quantity of their diet. The only thing they changed was the length of their eating window. 

One possible explanation for the positive results experienced by the study participants is that the shorter eating window did not allow for late-night snacking, which is a time when a lot of mindless calories can be consumed.

With that in mind, we have some evidence that eating right before bed and then pushing your fast into the next afternoon might not be as beneficial for weight control as starting your fast after dinner. 

Eating at night: yes or no?

Late Night Eating and Hormones

Another strike against late-night eating has to do with hormone production that occurs in a predictable why throughout the day. For instance, melatonin is a hormone that naturally increases in the evening hours. It plays an important role in your sleep pattern and signals the pancreas to slow down insulin production (2).

Therefore, if you eat a big meal late at night your blood glucose level could remain elevated throughout the night because there is not enough insulin to remove it.

If you follow my 0,1,2,3 strategy, you know that the “3” stands for three hours before bed, stop eating. This is a gentle, but effective way to stop late-night snacking. You can learn the 0,1,2,3 strategy here.

Fasting and Your Circadian Clock

Another benefit that comes when you start a fast earlier in the evening is that it promotes a healthy circadian clock, which supports healthy weight loss.

Another study by Dr. Panda demonstrates how eating and sleeping patterns promote or disrupt your circadian rhythm. Below is a graphic from the study that illustrates how a disrupted clock makes weight loss challenging (3).

fasting and your circadian clock
~source: Manoogian and Panda

We see from this graphic that a disrupted clock contributes to insulin resistance, poor sleep quality, and other metabolic problems like fatty liver. These factors can stand in the way of your body’s ability to burn fat.

Fasting and Shift Work

We also see from the graphic above that shift work disrupts a healthy clock. There is no doubt that working when your body would rather be sleeping is less than ideal from a metabolic standpoint. However, Dr. Panda addresses fasting and shift work in an interview conducted by Dr. Rhonda Patrick.

In the interview, he shares that research conducted on animals demonstrated that even when day and night routines are reversed, benefits are gained when calories are consumed in a shortened eating window.

If we look at this from the view of shift work, we can speculate that a shift worker is better off eating within a shortened eating window. But, the benefits may be dependent on getting adequate sleep when the worker is off duty. 

shift workers benefit from intermittent fasting

Timing a Fast and Sleep Quality

Another reason to start a fast after dinner, rather than eating late at night has to do with sleep quality. When you eat late into the evening, blood flow is directed toward your stomach. This central blood flow causes your core temperature to rise, making it harder to fall into the deep sleep needed for quality rest. 

Starting your fast at least three hours before bed promotes a robust circadian rhythm that allows you to get a good night’s sleep and wake well rested, feeling lighter and more energetic. 

start your fast at least three hours before bed.

Thank you for reading and have a wonderful week!

References: 

(1) Gill, Shubhroz, and Satchidananda Panda. “A smartphone app reveals erratic diurnal eating patterns in humans that can be modulated for health benefits.” Cell metabolism 22.5 (2015): 789-798.

(2) Mulder, Hindrik, et al. “Melatonin receptors in pancreatic islets: good morning to a novel type 2 diabetes gene.” Diabetologia 52.7 (2009): 1240-1249.

(3) Manoogian, Emily Nc, and Satchidananda Panda. “Circadian rhythms, time-restricted feeding, and healthy aging.” Ageing research reviews 39 (2017): 59-67.

About the Author:

Dr. Becky Gillaspy, DC graduated Summa Cum Laude with research honors from Palmer College of Chiropractic in 1991.

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