Circadian Eating For Better Fat Loss, Hormones, And Health

"Calories in - calories out are ALL that matter for fat loss!"

"Just hit your macros for the day, and you're good."

I've said both of the above to clients in the past.

But, as my knowledge of nutrition has grown as a coach, I've realized that there's a lot more to helping you as an online client achieve optimal fat loss and health than just macros.

My goal with this blog is to educate you on what you can do within your nutrition to achieve more fat loss, better hormones, and more optimal health - specifically in relation to your circadian rhythm.

This is especially relevant to you if you're someone that works odd hours (night shift worker, nurse, etc.)

Ready for a deep dive into the science that will help your results and overall health big-time? Let's get into it.


A weird amount of our biological processes are very rhythmic or cyclical.

Chronobiology - "a field of biology that examines periodic (cyclic) phenomena in living organisms and their adaptation to solar- and lunar-related rhythms. These cycles are known as biological rhythms." (1)

Chronobiology is basically the study of biological processes that have time-based rhythms - for example: the hibernation and wakefulness cycles of animals.

For more relevant examples to you as to why chronobiological processes are so important, consider...

→ The Wake/Sleep Cycle - We need this to happen in a cyclical manner. Spending too long in one phase (wakefulness or sleep) without cycling to the other is detrimental to your health. This is a big part of why I have online clients track their hours of sleep every single night - it's just too important to your overall health to ignore.

→ The Light/Dark Cycle - Constant light exposure creates sleep disruptions (more on this later). If you're constantly in the dark, you'll basically turn into Gollum. Again, too much of either is detrimental to your health.

→ The Feeding/Fasting Cycle - Constantly feeding? You'll soon be obese. Fast too often and you'll lose lean body mass, and eventually starve.

→ The Activity/Rest Cycle - So I think you get the idea by now, but we need both activity and recovery to create a strong, healthy body.

The point of all this is, there are tons of cycles and rhythms within your body that are vital to your health.

Circadian Rhythm

Within the study of all these rhythmic biological processes, we have something called a circadian rhythm.

Your circadian rhythm relates to biological processes in your body that seemingly run on a (roughly) 24 hour clock - meaning that many processes in your body repeat ever 24 hours.

Circadian rhythms aren't exclusive to humans. They're also present in plants, animals, fungi, and cyanobacteria.

Now, your circadian rhythm is endogenous, meaning that it originates from within your body and brain. That said, many external factors can influence your circadian rhythm to a large degree.

When your circadian rhythm is out of sync with the 24 hour day, this can create some major issues - which is what we're addressing today.

The Body Clock(s)

As mentioned, our circadian rhythm is basically set on a 24 hour "clock".

Now, we actually have multiple "circadian clocks" that are responsible for setting our circadian rhythm.

→  Our main circadian clock - the Big Ben of your biological rhythms - is located in the brain. This clock's "setting" can be affected by:

  • Light
  • Sleep
  • Shift Work
  • Activity
  • Different bed/wake times
  • Traveling to different time zones

Any of these factors can have a big impact on your brain clock's setting.

That said, we also have many peripheral circadian clocks located throughout the body:

→ Muscle - Affects insulin sensitivity

→ Pancreas - Affects insulin secretion

→ Heart - Affects cardiovascular processes

→ Intestines - Affects absorption of foods

→ Adipose Tissue - Affects fat accumulation

→ Immune System - Affects Inflammation

Now, since most of these peripheral clocks are related to food, when you consume nutrients can also help set their rhythms.

So My Body Has Clocks... Why Does It Matter?

So, when all of our "clocks" are in sync, we're in a state of circadian alignment - this is good. Hormones, sleep, digestion, etc. are all more optimal.

That said, by exposing our bodies to different light exposure, traveling through time zones, and even eating at much different times, we can create circadian misalignment. Basically, while your circadian rhythm comes from within, if certain behaviors don't align with this endogenous rhythm (think: light exposure, meal times), things can get out of whack.

In a state of circadian misalignment, your brain's circadian clock is no longer synced up with your body's peripheral clocks. This creates a lot of issues.

The Problem With Circadian Misalignment

So far, all of this has probably seemed like a lot of abstract concepts that aren't really relevant to you... so let's explain why your circadian rhythm is so damn important for your fat loss, hormones, and health.

→ Disrupts Body Temperature & Melatonin Cycles - Both crucial to the wake/sleep cycle.

In a state of circadian alignment, your body temperature is higher during the day and dips at night. Melatonin (a hormone that tells your body when it's time to sleep and wake up) works on an opposite schedule for healthy individuals, staying low during the day and rising at night.

Disruptions to these cycles obviously causes issues with sleep, leading to increased cravings for processed foods (2), decreased energy expenditure, lower training performance, and increased cortisol.

→ Decreases Leptin - Leptin is a hormone produced by your fat cells. Your leptin levels essentially determine how hungry your are, and your energy expenditure. When leptin levels are higher, hunger stays low and you expend more energy.

In the 2009 Study Adverse Metabolic and Cardiovascular Consequences of Circadian Misalignment, the authors found that circadian misalignment can decrease leptin by up to 20%. Basically, the equates to you feeling more lethargic and burning fewer calories throughout the day, along with increased hunger.

→ Increases Cortisol - Cortisol is "the stress hormone". Some cortisol is necessary - your body uses cortisol to wake you up in the morning.

The natural cortisol curve your body follows in circadian alignment has your cortisol levels highest first thing in the morning, and decreasing throughout the day to have you ready for a night of deep sleep and recovery before another cortisol spike in the morning.

Being in circadian misalignment essentially flips this curve on it's head, which can very well mean way too much cortisol. This can create hormonal imbalances, increase hunger, majorly disturb sleep, and cause a variety of other issues. (3)

→ Increases Blood Sugar & Insulin Response After Eating - When in circadian misalignment, you have a much worse blood sugar response to a particular meal, the insulin response to handle glucose is also much higher - essentially meaning you're more insulin resistant.

Crazily enough, studies have shown that the blood sugar response to the exact same meal was much worse for people who woke up at 8pm (circadian misalignment) vs. those that woke up at 8am (circadian alignment). (3)


→ Circadian disruption creates an increased risk of metabolic disease - This is especially true for shift workers. A meal you eat at night is metabolized much differently. As mention, the blood sugar and insulin response to a meal is much different at 8am vs. 8pm. The same is true for 4am vs. 4pm.


Chrononutrition relates to the timing of your nutrition. Let's talk about how you can manipulate it for a better circadian rhythm, fat loss, and health.

First, let's start with a few things we know about chrononutrition:

→ People tend to have very erratic eating behaviors - Meal times and caloric consumption are all over the place on any given day. This typically includes a prolonged eating window (15-16 hours) with people eating upon waking, all the way to bed time. People also tend to eat thier first and last meal a few hours later. Since meal-timing is important for the peripheral clocks, this contributes to throwing things out of sync.

This fact aside, I've found that as a new online nutrition client, one of the most impactful things we can do for your fat loss is simply establishing a specific structure to your day based around eating 3-4 whole-foods meals.

→ Consistently fasting until the afternoon might not be the best idea - With the above point in mind (the poor glucose and insulin response to eating at night), fasting for a big chunk of the day might not be the best idea. Not that fasting in itself is "bad", but it likely pushes a large chunk of your calories to later at night.


→ We see a difference in your beta cell  (cells that produce, store, and release insulin) function from morning to evening

→ You experience more rapid gastric emptying in the morning vs. the evening -  Basically, your stomach empties faster. (4)

→ Post-meal energy expenditure seems to be higher in the morning, whereas calories burned during digestion can actually be up to 44% lower in the evening - A 2014 study had one "breakfast group" eating 700 calories for breakfast vs. another group skipping breakfast entirely. After 6 weeks, there were no differences in body composition between the two groups, despite the breakfast group eating ~560 calories more daily. This is due to the breakfast group experiencing increased physical activity expenditure and calories burned during digestion. (5)(6)

→ Consistent meal times improves insulin sensitivity and calories burned during digestion - A 2016 study compared two groups: one ate 3 main meals 3 snacks daily for 2 weeks. The other group varied between 3-9 meals every day for 2 weeks. The results? Lower glucose response and increased thermic effect of food in the consistent meal-times group. (7)

(Full disclosure: many of these are Danny Lennon's observation's - his lecture at The Ultimate Evidence-Based Conference 2019 was my primary source for this blog. I can't give him enough credit.)

Applying Chrononutrition For A Better Circadian Rhythm, Fat Loss, Hormones, And Health

So at this point you might be asking...

"What the hell do I do with all of this?!"

First and foremost, realize that the idea of chrononutrition is relatively new - within nutrition coaching, we can apply many of these concepts very confidently, but none of it is set in stone.


→  Eating at "biological night" seems to be worse for your metabolic health - It's likely a good idea to stop eating 2-3 hours for bed.

→ Natural light exposure early in the morning is important for your circadian rhythm - Even on a cloudy day, Lux (light intensity) is much higher with natural light intensity than artificial.

→ Consuming some nutrients during the first few hours of your day is probably a good idea for your circadian rhythm - COFFEE DRINKERS: caffeine qualifies as a nutrient ;) As a whole, there seems to be good evidence that eating more of your calories earlier in the day is a good idea (as opposed to the typical intermittent fasting protocol of pushing your calories to later in the day).

→ Establishing consistent meal-times is more optimal for your metabolic health, and increases fat loss - SHIFT WORKERS: This means that establish a meal-schedule during the day and sticking to it - even if it means not eating at night when you're working - seems to be more optimal for health and fat loss.

→ If trying to follow these principles makes it harder your you to stick to the foundational principles of good nutrition (e.g. consuming quality foods, calories aligned with your goals, etc.), you don't have to follow these strategies - in this case you'll get better results if you don't.

The reality is, calories and macros are still king. We can't overrule the concept of energy balance for fat loss.

That said, for overall health, it's a lot more than just hitting your macros. Educating you on things like chrononutrition is one of the most impactful things I can do as a coach, to help you create a leaner, stronger, and more confident version of yourself.

Really, there is so much that we can do within nutrition coaching using cool concepts like chrononutrion to help you burn more calories, create better hormones, achieve your ideal body composition, and bring a better version of yourself to the world.

Calories and macros are king, but they're far from the only thing that matters in helping you achieve your optimal body composition. Within nutrition coaching, we go much deeper than that to create the best version of you.

About The Author

Jeremiah Bair is a certified nutrition coach, strength coach, and owner of the Online Coaching Business Bairfit. His Instagram is noticeably missing any calf pictures.

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