Intermittent Fasting Might Not Be For You... But What About Circadian Eating?

Intermittent fasting has been all the rage. With enticing promises like fat loss, increased metabolism, better blood sugar management, reduced inflammation and improved brain function to name a few, it is not surprising that people are flocking to this way of eating. There are a variety of approaches to intermittent fasting, some restrict eating to certain hours of the day, some restrict eating to certain days of the week and others use a combination of the two methods. Each approach has its own pros and cons and is linked to different health benefits.


Unfortunately intermittent fasting isn’t right for everyone. Like any diet or way of eating, everyone will have a different experience. Similar to any major lifestyle change, it is helpful to have a trial period to see how your body responds and how you feel on it, before fully committing to it. For some people, I would even suggest avoiding the trend all together.


For women who are feeling stressed and burnt out, intermittent fasting likely isn’t ideal. As you can imagine, not eating for extended periods of time stresses our body. Although small, controlled doses of stress can help your body adapt and become stronger and more resilient, if your body is already dealing with a myriad of stressors day-to-day, it may be too much to handle.


Plus, stressed, burnt out women often have issues with managing their blood sugar as is. This is because cortisol, our stress hormone, can cause both blood sugar spikes and elevated blood sugar in the long term. If this is not well managed before starting intermittent fasting, combining these surges in blood sugar, with extended periods of fasting, where the blood sugar is depleted, will leave you on a blood sugar roller coaster. This can leave you feeling exhausted, irritable, anxious, reliant on pick-me-ups like coffee and sugary snacks and can have you struggling with managing your weight.


So what if you want to experience the benefits of intermittent fasting, but don’t want to without doing further harm to your body? Circadian fasting, a more moderate approach of fasting, might be a more suitable option.


Circadian fasting uses the sun as your guide for when to eat. If the sun is up, feel free to eat, and if the sun is down, consider giving your body a break from eating. In intermittent fasting terms, your feeding window is from sunrise to sunset and your fasting window is from sunset to sunrise.


As you can imagine this way of eating is often not a lot less restrictive as many other intermittent fasting approaches. Also, the extent of fasting varies throughout the year, which can help your body and your metabolism to be more adaptable than sticking to the same schedule year round. With more hours of sunlight in the spring and summer, you will have longer feeding windows and shorter fasting windows. In the winter and fall, when we have relatively fewer hours of sunlight, you will have shorter feeding windows and longer fasting windows. Where I am in Canada, in December, when we have the fewest hours of sunlight, the sunrises around 8am and sets around 5pm, this would mean roughly a 9 hour eating window and 15 hour fasting window. However, in June, when we have the most hours of sunlight, the sunrise around 5:30am and sets around 9pm, this means a 15.5 hour fasting window and 8.5 hour fast.


Through circadian fasting you are not only aligning with the rhythms of the sun, but also your body’s own natural rhythms which are also guided by sunlight. Our internal 24-hour circadian clock determines the timing of a variety of our body's functions, including when we sleep, when we are hungry and when certain hormones are released.


Based on our circadian rhythm, our bodies are not designed to effectively digest and absorb nutrients later in the day after the sun is down. This is meant to be our body’s time to rest and repair. So when we eat after sun down, our body does not handle it as well as it would during the day. We can eat the exact same meal during the day when the sun is up and in the evening after the sun is down, and it can produce a completely different response in our body. The meal after sundown will lead to higher blood sugar spikes which can negatively impact your energy levels, mood, metabolism and your sleep.


If you are intrigued by how your body will respond to eating in a way that is more align with your body’s internal clock, use these guidelines can help support your journey:

Try to eat within the first 1 hour after sunrise.


Try to eat before sunset. It is best if your last meal of the day is at least 2 hours, ideally 3 to 4 hours, before bed to allow for proper digestion and reduce the impact of that meal on your sleep.


When you first start, do not go beyond a 12 hour fast. Regardless of what time of year you start circadian fasting, do not start out with more than a 12 hour fasting window if you have not been eating this way previously, as it might be too much of change for your body to handle. Start with a 12 hour fasting window, then adjust your window by 30 minutes each week, as needed.


Adjust your eating windows every season as daylight changes. Your eating window does not need to change day-by-day as daylight changes, but adapt your schedule every month or so.


Be flexible with yourself. You should use sunlight as a rough guideline, if it doesn’t fit your schedule everyday that is okay.


Avoid day long or multiple day fasts. Extended fasts will likely be too much for your body to handle in your current state.


Listen to how your body responds. If you try circadian fasting and you find it makes you feel tired, cranky or some other undesirable way, it might not be for you, at least not for now. Additionally, if you have a history of disordered eating and you find having guidelines around eating is reverting you to your previous ways of disorder thoughts or behaviours, you should stop following the guidelines immediately.


Just like any other lifestyle change, start slow, give yourself some grace and listen to how your body responds to the change. If you give circadian fasting a try, let me know how you find it, how your body responds to it and any challenges you have experienced.


Want to learn more?

Check out this blog on how to reset your sleep schedule using a circadian approach.