Fasted Workouts and Fasted Cardio vs EPOC – For Fat Loss

January 30, 2009

There are two schools of thought when it comes to losing body fat. The first approach is to focus on utilizing as much fat as possible during your workout, by going into your workout in a fasted state. The other approach is to not worry about fasting and focus on intensity to burn more calories around the clock after the workout is finished (EPOC). Let’s talk about the benefits of both, as well as something significant that rarely gets mentioned.

mountain lion hunting
[When an animal is in a fasted state, something interesting happens to give that animal an energy boost. This boost of energy gives the animal the ability to reach peak performance even when it hasn’t consumed a calorie for long periods of time. We will talk about how and why this is significant later in the post.]

The Argument For Working Out in a Fasted State

Anyone who has read my blog for any period of time, knows I recommend to do your workouts in a fasted state. The problem with eating before working out is that you are simply burning food energy vs body fat for energy. Plus…eating releases insulin, which interferes with your body’s ability to burn body fat. Basically, eating before your workout gets in the way of burning body fat during your workout.

The Argument Against Working Out in a Fasted State

It seems like “a no brainer” to workout in a fasted state…but it isn’t that simple! Intense training has been shown to increase the calories burned long after to workout is over. In fact, it is possible to burn an extra couple hundred calories after an intense workout. Those who argue against working out in a fasted state, claim that you will not have enough energy to have an intense workout. This seems logical on the surface, but the body is smarter than that…

sympathetic nervous system SNS

[An exciting picture of neurons! Actually, it is a pretty cool picture of the nervous system. Who would have thought that was possible?]

Your Sympathetic Nervous System = Energy in A Fasted State

For the longest time, I didn’t understand why I had more energy after fasting. I have my most productive hardcore workouts after fasting for 5-18 hours. If I ate anything in that 4-5 hour window before training, the workouts just weren’t as intense. Ori Hofmekler explained where this “hidden” energy source came from…the Sympathetic Nervous System (SNS).

Why Does The SNS Kick In When in A Fasted State?

Ori explains it best…

“When fasting, a primal survival mechanism known as the fight-or-flight reaction to stress is triggered, maximizing your body’s capacity for generating energy, being alert, resisting fatigue and resisting stress. The survival mode is primarily controlled by a part of the autonomic nervous system known as the sympathetic nervous system, or SNS. When it’s in gear, the body is in its most energy-producing phase, and that’s when the most energy comes from fat burning.”

This makes sense, because as hunters and gatherers our ancestors needed to be at our peak performance when hungry in order to catch the next meal (kind of like the mountain lion pictured above).

Eating Before Working Out Interrupts This Surge of Energy

Ori explains how the Parasympathetic Nervous System slows you down after a meal. Note: In the article I’m quoting he is talking about morning meals and not eating before your morning workout…

“If you do eat a breakfast of, say, bagel, cereal, egg and bacon, you’ll most likely shut down this energy-producing system. The SNS and its fight-or-flight mechanism will be substantially suppressed, and your morning meal will trigger an antagonistic part of the autonomic nervous system known as the para sympathetic nervous system, or PSNS. The PSNS will make you sleepy, slow and less resistant to fatigue and stress. Instead of spending energy and burning fat, your body will be more geared toward storing energy and gaining fat.”

Ori, recommends mainly eating at night after your physical activities are done for the day. He claims that food makes your body relax and prepares the body for sleep.

You Can Have an Intense Workout While Fasting

As I stated earlier, I have a better workout in a fasted state. Not only do I have more energy, I don’t burp up a meal when doing an intense interval or circuit. So, my argument is that working out while fasting allows the body to burn more calories during AND after your workout.

Note: Just like the rest of my site, there are no “absolutes” here. There are a lot of approaches to get lean, this approach just makes sense to me (and it flat out works). The majority of you have already read my approach to cardio, but if you haven’t…here is a little mini-course I threw together: Low Body Fat Cardio

Important Message: Although this site has received 25+ million visitors, I am starting from scratch and abandoning it. This site is dated and old school looking, terrible to read on mobile, etc.

It's like a Ford Pinto compared to my new site...which is like a Ferrari. Click the link to head over to my new site.

Starting Over...R.I.P. Fitness Black Book!

Thanks for reading all these years!

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{ 6 comments… read them below or add one }

Chastina July 13, 2012 at 10:03 am

Greetings Mr. Moore,

I am so happy I found your blog. I have been criticized all my life for eating the way I do (I only eat when I am hungry and I hardly ever need food before workouts) and, even though I have always been very fit, some have even said I have an eating disorder…5’9 and 155lb, I do not have an eating disorder.

I find it a little funny that friends and gym patrons will ask me about my eating habits (stating that they are lost and confused about nutrition) but as soon as I start to go over how I eat they become instantly dismissive, and some even flip from inquisitive listener to disapproving nutrition experts; “No wonder you are so thin, you are starving yourself!”

I recently started training again and I love my gym but the trainers there are…well, they do not have the same views. I work with a trainer (and even though I explained my way of life and eating, he still pressed that I should stick to his plan) and the eating regiment he put me on was making me sick, as well as made me incredibly lethargic during my workouts (not to mention it felt like I had a rock in my stomach), and worst of all I gained 10lbs in the three months of training. I sat down with my trainer and we agreed that I was getting stronger (can easily pull a sled with 500lbs on it) but I was not slimming down, I was bulking up.

I have been trainer free for 5 weeks now and I dropped the 10lbs, my energy is sky high, and my skin is glowing. My boyfriend told me that I was being too patient with the trainers and should have dropped them right away…should have listened to him.

I like my gym and I really do love my the employees there (great people) and because they are great people communicating that my style of fitness is different but not wrong is easily accepted by them…if only because of the speedy change they have witnessed first-hand.

It is refreshing to read that there are others like me and to see how fit they look as well. Thank you for posting such an interesting blog on a subject most choose to ignore or dismiss. I also love all the responses, great questions.


stacy August 6, 2012 at 3:45 am

In theory I love the idea of working out in a fasted state/first thing in the morning. However, in practice I’ve found my performance is terrible, I get dizzy, see stars, and generally have a horrible workout.

If I exercise around sunset, I’m terrific.

My question is if it’s been 5-6 hours since you’ve eaten, is that still a ‘fasted state,’ or must it be a full 12 or so?

I am only going by anecdotal evidence, but I find men in general have a much easier time with surviving hunger. Most women I know need to eat frequently.

Jason August 26, 2012 at 2:30 pm

Stacy, how much are you eating during your window the day before? If you do not consume enough healthy calories your body will most definitely shut down mid workout. Also, what are you eating during your window? (window being the time between fasting where you consume your food for the day.) Also, how much water are you taking in daily? I have not heard of anyone having the same issues you describe.
If your already at a healthy body weight.

To awnser your question, from my research I am finding most people describe thier “fasting time” as anywhere from 8-24 hours pre workout. 5-6 hours is most likely not enough time, try timing your fasting time so that you can sleep during the majority of it. Remember water is ok during your fasting, a big gulp will curb any hunger pains temporarily before bed. In some extreme cases I will also chew gum to help.

Jason August 26, 2012 at 2:39 pm


Thank you so much for this post. As someone with a very busy schedule (new baby, 2 jobs, student) eating HEALTHY snacks every 2-3 hours is nearly impossible. I really like the idea of IF and started it yesterday after a few hours of research. I found this blog post to be the most effective and to the point for information.

I stopped eating last night at around 9pm, and woke up today and left for a long hike and bike at around 10:30. I must say, I was shocked at the results. I felt as though I had endless stamina and energy. I did not feel sick or hungry at all. And for some reason even found myself rarely reaching for my water bottle. It blew me away. I really like the idea of this approach and plan on sticking with it for the next 4 weeks to see how it turns out. I just have a few questions for you, I will try to keep them short and to the point. My goal is to shed this horrible spare tire ive been carrying for the last 8 years. I have lost a total of 65 poounds, but cant seem to shake off this stored fat. Im hoping IF will help.

Is it ok to plan my daily eating around IF? if so, should I take one day a week where I attempt to eat regularly?

Is a small amount of caffiene ok pre workout? I find that it makes a world of difference for me in my morning workout, as I am not a regular caffiene user.

And finally, what is the deal with these “sugar substitutes” are any of them “healthy” in the sense that they dont trigger insulin response the same as normal sugar?

Thank you for your time, I look forward to reading more of your posts! keep it up!

Jason August 26, 2012 at 3:02 pm

Thank you Mark Sisson, found the awnser to my question regarding artificial sweeteners.

Fitness Wayne | Paleo and Strength Training November 20, 2012 at 8:34 am

I have been paying more attention to this lately because I have been doing a lot of fasting to get lean. I have noticed a decrease in performance when I fast but I think it might be a mental barrier holding me back.

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