Chrono Diet: the new circadian fasting?

Heard of the Chrono Diet? Me either. That is, until I realized it was just another way to describe circadian fasting.

Circadian fasting is all about when we eat. 

Our bodies are aligned with a 24-hour clock, that syncs with the Earth’s rotation facing towards and away from the sun each day. 

The body’s hormones naturally increase and decrease depending on the time of day. 

When we eat should be in sync with our circadian rhythm.

Chrono Diet Explained

Chrono Diet, or Chrono Nutrition is aligning your eating window with your body’s circadian rhythm (1). For most of us, this means eating during daylight hours.

Chrono nutrition has roots in Eastern and alternative medicine but is an emerging science. In the last 10 years, interest in chrono nutrition has grown as a means to reverse metabolic diseases (2).

The Chrono Diet recommends a 12-hour eating window that syncs with daylight hours.

Of course, this may not be the case during winter or summer hours depending on where you live.

Our bodies still follow a 24-hour clock regardless of how daylight changes throughout the year.

The important part is to pick a 12-hour eating window during your waking hours.

Circadian Rhythm Char

If we eat in alignment with our circadian clock, our metabolism is efficient and hormones are in balance.

When we eat in a manner that is not in alignment with our natural circadian rhythm, there are metabolic consequences.

These metabolic consequences include elevated blood sugar, high blood pressure, weight gain, sleep disturbances, body fat accumulation and more.

This circadian rhythm chart is the foundation of circadian fasting.

Circadian fasting is using our natural circadian rhythm to help us find the best time to eat.

Circadian Hormones You Should Know


Cortisol is your “fight-or-flight” hormone. When this hormone is elevated, heart rate increases, blood pressure increases, blood sugars rise, inflammation is elevated (3).

Cortisol rises in the morning to help us prepare for the day, this is a natural part of our circadian rhythm.

When stress is high, cortisol levels may stay elevated at night.

Elevated cortisol negatively impacts sleep and recovery. Prolonged cortisol can cause increases in abdominal body fat.


Insulin is the hormone that regulates blood sugar, it moves blood sugar out of the blood stream and into the cells.

Insulin Resistance: A Halloween Story

The term insulin resistance means your muscles, fat, and liver aren’t as receptive to insulin (4). This is seriously problematic in the body. Let me explain.

Imagine you live inside your liver. It’s the day after Halloween. Your neighbor (insulin) wants to drop off their leftover candy (blood sugar) to your kids.

Here’s the problem. Your kids have been consuming unspeakable amounts of sugar for the past week from parties, sneaking candy from the stash and trick-or-treating.

You are like “oh hell no,” we are all stocked up here, you are not giving us any more sweets. I don’t care if it is the good stuff.

Your neighbor is ringing the doorbell, knocking, calling your name. Maybe they end up slipping some candy in the mail slot, because that happens.

But you are not opening the door. You look out the window and see your other neighbors walking up to your door with even more candy.

Except now, everyone is starting to get upset and cause a scene (inflammation). They are throwing candy in your yard, stepping all over your flowers. Meanwhile, you’re mad, they’re mad, your kids are crying and the whole situation is a mess. This is insulin resistance.

The goal here is to not let everyday be a “day after Halloween.” It causes major metabolic drama in the body. This is how we get fatty liver disease.

Insulin Sensitivity

We want our cells to be insulin sensitive. We want to not have so much sugar already stored in our cells that when insulin comes knocking, it’s no big deal to take a few extra pieces of Halloween candy.

When insulin sensitivity is naturally low in the evenings, then it is not a good time to have carb-heavy meals.

Growth Hormone

Growth Hormone maintains the body’s metabolism and helps repair muscles and body tissues. It also helps regulate blood sugar levels and lower inflammation.

Fasting has a profound effect on the production of growth hormone.

One 24-hour fast can increase human growth hormone by nearly 1,000%-talk about a metabolic boost! (5)


Melatonin is the “sleepy” hormone. This hormone responds to light exposure. After sunset, as the eyes are exposed to less light, the body starts to produce melatonin.

If you are looking at mobile devices or have bright lights on in your home in the evening, this can delay, or impede the production of melatonin.

Conversely, melatonin decreases in the early morning hours to help the body feel more awake and alert.

Circadian Fasting and Time-Restricted Eating

Circadian Fasting and Time-Restricted Eating are both types of chrono nutrition. They are based on aligning your eating window with your circadian rhythm.

Circadian Fasting

Circadian fasting involves restricting your eating window to waking hours.

Waking hours roughly translates to a 12-hour eating window. This could mean your eating window is 7am to 7pm.

Circadian fasting is how we all should be eating, regardless of whether you try intermittent fasting.

Trying a 12-hour eating window can also be a good introduction to time-restricted eating.

Time-Restricted Eating

Dr. Satchin Panda champions time-restricted eating with his revolutionary work on circadian rhythm and eating windows. (6)

Time-Restricted Feeding is compressing your eating window to 12 hours or less.

Dr. Panda’s early research indicates that time-restricted eating helped reverse metabolic disease, aging, and reduced risk factors for chronic disease. (7)

One important note is that time-restricted eating doesn’t necessarily include calorie restriction, it simply refers to eating in a smaller eating window.

You can discover more about the different types of fasting in one of my first blog posts.

Getting Started with Circadian Fasting

Step 1: Determine your usual waking time and bed time. Pro tip: consistent sleep and wake times are ideal for circadian rhythm.

Step 2: Pick a 12-hour eating window during your waking hours.

Step 3: Consume all your calories from foods and beverages in that window. Pro tip: for sleep optimization, close your eating window 2 to 3 hours before bed.

Step 4: Set up a FREE preview session with me and we can set your eating window together.

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Hi, I'm Shannan.

I help adults make confident choices for a lifetime of good health.


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