Is intermittent fasting just a trend? Is it legitimate? Is it too extreme? Is it starvation? Does it even have health benefits?
Intermittent fasting (IF) as a concept has been around since humans have walked the Earth. Of course, in the early days it wasn’t a concept, but rather a way of life. Our earliest ancestors had limited food availability; they were naturally in a fasting state because they couldn’t access food readily.
Today, we have the science to show that when the body runs out of sugar, cellular restoration happens. When you go into a fasting state, you start to deplete the levels of stored glucose in your body and use fat as your source of energy. This switch (from glucose to fat) is referred to as “metabolic switching.”
Once you get your body to this switching state, adaptations can start to occur: anti-aging pathways turn on, cholesterol levels improve, blood pressure goes down, and insulin resistance decreases.
For many of us today, though, food is available 24/7. We don’t take breaks from eating. In fact, we’re encouraged to eat often. So the thought of fasting (in the more traditional, daily fast) can seem daunting, even impossible. Is there another, easier, more sustainable way to do it?
What is Circadian Fasting?
You’ve heard of the circadian rhythm: your own, natural 24-hour internal clock that regulates your sleep-wake cycle. If you apply your eating patterns to that same clock, you get circadian fasting—short, logical breaks from consuming food at times that support your circadian rhythm. Circadian fasting is also sometimes called the “sun cycle diet” because you’re timing your meals with the rise and fall of the sun.
This is just one type of intermittent fasting (there are many to choose from), and you may already be doing it without even knowing it.
Circadian fasting can be easily implemented into your life without much change to your daily routine. Ultimately, the goal is to limit your eating windows. Typically, Americans eat for nearly 15 hours each day. Those 15 hours aren’t constant eating; that time frame includes the time our cells are working to metabolize the food in our system. We can give our cells a break by cutting down our windows of eating.
How to Start Circadian Fasting
You can start circadian fasting simply with a 12-hour fast. This is one of the most popular ways of fasting (and you may be doing it already): you begin your fast around 7 p.m. and fast until 7 a.m. (or any 12-hour timeframe). You’ll be sleeping the majority of those 12 hours, and then you can break your fast with some nuts or eggs and avocado.
You then eat your normal meals until dinner and stop eating again at 7 p.m., then start over for another 12 hours of fasting. The key here is to ensure you don't eat after dinner (no more late-night snacking), which can be difficult at first. You can distract yourself at night with simple workarounds, like a post-dinner walk around the neighborhood or putting your kids down for bed.
Continue on with this 12-hour fast for about two or three weeks, at which point fasting for 12 hours will probably feel pretty natural.
Once you become accustomed to this shorter fast, you can increase your fasting period to the 16-hour fast. Using this approach, it’s common to fast from after dinner until lunch the next day. Once you hit this fasting window, you’ll begin to reap the benefits of metabolic switching and intermittent fasting.
It’s at this 16:8 mark (16 hours of fasting, 8 hours of eating/metabolizing) that you’ll start to see improvements in your overall health, including your blood sugars. If you’re on insulin, you may even start to need less insulin.
Last but not least, there are no hard rules except that you need to listen to your body. If you can’t go the full 12 or 16 hours, don’t worry—there’s always tomorrow! You can slowly ramp up your fasting window each day. Try adding on 15 or 30 minutes each day; slowly and surely you will reach your fasting goal!
This article has been clinically reviewed by Hanna Rifkin, RD, CDCES, clinical health coach at One Drop.