The Mental & Physical Health Benefits of Circadian Fasting + Simple Schedule Tweaks That Can Boost Your Mood & Reduce Stress with Dr. Amy Shah

I am sure by now you have heard of the benefits of intermittent fasting. But can skipping meals or only eating during certain time periods really improve our health? In this podcast (episode #228) and blog, I speak with intermittent fasting expert Dr. Amy Shah about how fasting can greatly improve your mental and physical wellbeing, the different types of fasting, why Dr. Amy prefers circadian fasting, how women can fast safely, common fasting mistakes, how to get started, if fasting is safe for people with eating disorders, and more! 

When it comes to our health, what we eat, how we eat and our other lifestyle choices can have a dramatic impact on our gut health, which, in turn, can impact the brain and body. The gut-brain connection is incredibly powerful. If your gut is inflamed and you fix that, your brain will feel better, and vice versa.

Even though we are learning more and more about the gut-brain connection, our overall health and immunity, many people are not told about this when they are feeling ill or battling with their health. Yes, Western medicine is good for many things, but it doesn’t know everything!

One of the best ways to harness the power of the gut-brain connection to improve our mental and physical health is through intermittent fasting. Yet, before you just stop eating for several hours, it is important to understand that fasting impacts men and women differently. Unfortunately, most of the research is done on male animals—we are only now starting to study the different impact certain types of fasting have on women. There are many differences between the male and female body, including our hormones and how we process stressors, which need to be considered when we study fasting and how it impacts our overall health. There are also differences between each individual. When it comes when we eat and when we don’t eat, there is no “one size fits all”! 

Women are impacted more by stressors like long-term dieting, excessive exercise and aggressive, long-term fasting, which will disturb your hormones and health. That is not to say that women cannot benefit from intermittent fasting, but they need to be aware the risks of aggressive, long-term fasting on the brain and body. GnRH is the master hormone that is linked to our circadian rhythm—it pulses in accordance with this rhythm, telling the pituitary gland to release its hormones, which signals to the ovaries and adrenal glands to release hormones like estrogen in a feedback loop. In women, this system is very sensitive to external stressors. If we fast, exercise or diet aggressively, it affects the pulsing of the GnRH, which has repercussions throughout the brain and body. Some signs of this are: feeling fatigued, bloated or anxious, sudden mood changes, weight fluctuations, and upset sleeping patterns.

For most women, aggressive fasting can dramatically impact their hormones and affect their health in the short and long term, especially when they start fasting or do longer fasting intervals on a regular basis. We need to be very careful about listening to what we hear on the media or from the wellness industry! Long-term fasting is not for everyone, just like an Iron Man challenge or ultra-marathon is not for everyone. If you do decide to go this route, train for it, and monitor its effects on your health with the help of a medical professional.

We cannot escape the fact that how we live our lives affects our wellbeing. As Amy notes, our hormonal pulses and circadian rhythms are completely intertwined. Every cell in our body has a “clock” that follows these 24-hour rhythms. In fact, 80% of our genes are based on our circadian rhythm! Our bodies are meant to have a rhythm—we are not made to do everything at once.

When our circadian rhythm is out of whack, we can suffer from many kinds of health issues, including mood disorders, brain health problems, diabetes, heart disease and so on. On the other hand, if we tweak our schedule just a little bit and let our brain and body know when it is day and when it is night, we can improve our overall wellbeing by improving our sleeping patterns, metabolism, mood and so on.

Circadian fasting is one great way to tap into these natural rhythms and create an environment that boosts our mental and physical resilience. If we stop eating 2 to 3 hours before bed, this will prepare our body, telling it that it is nighttime and it should go into “gut repair mode” and deep clean the cells. This can only be done when we do not have more glucose from food entering our bodies. If we eat late at night or before bed, however, the body does not go into this deep clean mode, which can affect our health.

Circadian fasting also helps our body harness the power of the metabolic switch. The body generally uses sugar as fuel—this is its preferred source of energy. When we have used up all this glucose and the body needs energy, it switches fuel sources and uses stored fat (fatty acids). This is known as the metabolic switch, which turns on when we are hungry or fasting. When the body does this, it can have many downstream health benefits, such as suppressing excess inflammation, increasing stress resilience and improving cognitive function and emotional health.

Circadian fasting essentially trains your body to switch fuel sources. Yes, at the beginning this can be tough and we can feel a little off, but our body will get used to this shift over time. It is a type of good stress—circadian fasting gives the body a little push to get stronger, like a good workout. And it is a lot easier to do than many other fasting regimens because it can be incorporated into a busy schedule.

If you have battled with fasting in the past and are not sure how to make the process easier or effective, Amy has some great tips to help you harness the power of circadian fasting:

  1. Don’t start too extreme, as changing your eating schedule can be challenging, especially if you are used to eating late at night! Start from 7pm-7am, and slowly increase the number of hours you fast at night over time. Give your body time to adjust! You can also alternate the number of hours you fast for during the week—listen to what your body needs and find out what works for you. 
  2. Expose yourself to daylight first thing in the morning before 10 am for around 20 minutes, even if it is cloudy outside, which will help balance your circadian rhythm and boost your metabolic switch.
  3. Do a fasted workout/movement early in the morning. Get moving before you eat breakfast! But don’t push yourself too hard too quickly—find out what works for you and start there.
  4. Try get 7 to 8 hours of sleep at night. This doesn’t have to happen every night, but we should aim for good sleeping patterns around 5 times a week.
  5. Our peak eating times is between 12 and 5 pm, so you want to eat your main meals during this time. Eat a smaller meal before noon or after 5 pm if desired, and stop eating 2 to 4 hours before bed. 
  6. Eat lots of plant fibers, which help improve our gut health by feeding the good bacteria in the gut that are essential for brain health, immunity and hormone function.
  7. Around 2 to 3 hours before bed, turn off your artificial light devices, such as your smart phones or TV. It is also a good idea to switch the light bulbs in the bedroom to yellow light or use candle light. Research has shown that just one bout of bright light at night can delay your melatonin for up to 90 minutes!
  8. Avoid these common fasting mistakes:
  • Fasting too long.
  • Eating too much sugar in your eating window, which will make it harder for your body to turn on its metabolic switch, and, when your sugar levels fall, you will experience hunger cravings and jitters that will affect your ability to avoid eating and experience all the benefits of intermittent fasting.
  • Thinking that fasting is a shortcut or magic bullet that will take away all our issues. It is an important part of a healthy lifestyle, not a quick-fix solution

It is also important to remember that fasting may not be for everyone, especially someone with a history of disordered eating. Fasting is not generally good for someone who has a history of eating issues, especially if they cannot do it in a safe way, as it can trigger a restrictive eating response. In a situation like this, it is better to focus on what the person is eating, and how they can cut out processed and refined foods and improve their diet.

For more on fasting and mental health, listen to my podcast (episode #228) with Amy, and check out her website. If you enjoy listening to my podcast, please consider leaving a 5-star review and subscribing! And keep sharing episodes with friends and family and on social media. (Don’t forget to tag me so I can see your posts!)

This podcast was sponsored by:
BiOptimizers (The supplement to boost your gut health and improve your immunity this winter!): Use code DRLEAF10 for 10% off your order of the Bioptimizer’s Ultimate Immunity Stack at

For more self-care tips to improve your mental health, pre-order my new book 101 Ways to be Less Stressed, which is now on sale at 20% off! 

You can also check out my app SWITCH, which is a great tool for helping you learn how to manage your mind and go beyond mindfulness by dealing with the roots of your choices and overcoming thought patterns and behaviors that hold you back through the mental process of reconceptualization. 

To learn more about fasting and mental health, register for my Virtual Mental Health Summit this December 3-6! For more see CME and CEU credits are available for PAs, NPs, RNs, MDs, DOs, and other medical professionals, and certificates of attendance will be given for physical therapists, occupational therapists and social workers! 

Podcast Highlights

1:44 Why Western medicine doesn’t know everything  

4:13 Why the gut-brain connection is so important when it comes to our health

5:30 How is fasting different for women and men?

13:37 What is circadian fasting and why is it so good for us?

22:24 What is the metabolic switch and why is it important?

26:49 How extreme fasting impacts our health  

29:45 The dos and don’ts of fasting 

46:46 How certain types of fasting can be dangerous 

51:10 Common fasting mistakes many people make

54:27 Is fasting safe for someone who has a history of disordered eating? 

57:55 How fasting can improve our mental health

This podcast and blog is for educational purposes only and is not intended as medical advice. We always encourage each person to make the decision that seems best for their situation with the guidance of a medical professional.

Switch On Your Brain LLC. is providing this podcast as a public service. Reference to any specific viewpoint or entity does not constitute an endorsement or recommendation by our organization. The views expressed by guests are their own and their appearance on the program does not imply an endorsement of them or any entity they represent. If you have any questions about this disclaimer, please contact


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