Optimal Fasting & Feasting Windows

Optimal Fasting & Feasting Windows

The human body is complex, but at the same time, it can be very predictable. Our genes and our epigenetics hold a lot of important information that has taught us a ton about what to expect when we employ certain lifestyle interventions. An example of this is the timing of your fasting window. One popular approach is to just push your eating window back when you are intermittent fasting. It works well for a lot of people, but you may also consider another approach. In a 2018 study, the investigators studied the differences between meals consumed at 9am and 5pm. Keep in mind, this was 5pm, not 8pm or 9pm like a lot of us tend to do! In this study, they checked blood glucose at baseline, 30, 60, and 120 minutes after the meals. Postprandial (meaning after a meal) blood glucose was higher in the evenings. So what does that mean? If you understand circadian biology, you know that we are diurnal creatures. This simply means that our bodies are designed to eat during daylight hours, and sleep and do other fun activities at night.

In addition to attempting earlier feeding windows, it’s also important to have a predictable schedule. This is especially important if you have circadian biology issues—the main issue being sleep. You see, just like our circadian clocks are set by sun light, we also help establish these rhythms with the timing of our meals. A lot of us, and I have been guilty of this myself, have done one version of intermittent fasting for years. But we didn’t really know then what we know now, and that is the importance of establishing predictable feeding windows. We have a lot going against us in our modern lives. On one hand, we don’t have food insecurity like we used to have. So we can actually time our meals, and this is important nowadays because while we have solved a lot of problems with respect to hunger, we are now in fact on the opposite side of this issue—that is to say that we are now experiencing diseases of plenty. We eat too much, too often, and too haphazard.

Instead of switching feeding windows depending on your schedule, take just a little more time planning this out so that you can have a predictable window. This will improve your sleep and recovery, and more importantly put you in an environment that is much more conducive to fat burning. I’m not just speculating here. Listen to what the authors of this one study on the subject said: “Timed meals therefore play a role in synchronizing peripheral circadian rhythms in humans and may have particular relevance for patients with circadian rhythm disorders, shift workers, and transmeridian travelers.” So, if you are already doing some type of intermittent fasting, consider moving your eating window earlier in the day, and sticking to that schedule as closely as possible. If you’re an early riser, you could even do something as early as 8am to 4pm. If you want to try this, just understand that you may be accustomed to doing the later window and would probably have to adapt to this earlier window.

There are several benefits to this approach. First of all, if you could eat an early meal and postpone your coffee until lunchtime, you will allow your morning cortisol levels to drop before spiking them with that coffee. Secondly, you will likely have a better metabolic response to this earlier window, indirectly contributing to greater fat loss. Lastly, when you end your eating window earlier, you give your body more time to digest your last meal and even burn some of it off before sleeping, putting you in an environment that is much more conducive to fat burning, and likely improving your sleep quality.


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