What is Intermittent Fasting?

There are a lot of diets and eating plans out there, and as a former fat kid I’ve tried a lot of them. One of my preferred methods is called “Intermittent Fasting”, which adjusts your daily eating rhythms to promote healthy choices. Lets talk about what it is, some benefits you can get from trying it out, and how to do it.

Disclaimer: As always, please remember that I am a fitness professional but I am not a doctor. If you know you have dietary guidelines you need to follow for current medical conditions, follow those guidelines! If you have concerns about trying this, ask your doctor.

What is Intermittent Fasting?

Fasting is a pretty simple concept, and you do it every day. It’s a prolonged period of not eating, which causes specific metabolic changes to your body after a few hours. These few hours are spent processing the meal and using the stuff you ate to power the rest of your biological processes. The most notable here is the production of energy from using glucose in your blood stream (“blood sugar”). When you eat, especially when you include carbohydrates in your meal, the body will preferentially burn those bits of sugar before resorting to resources already in the body.¬† During periods of prolonged fasting (like when you’re sleeping, for instance) the body does not have this blood sugar to use for energy, so it is more likely to pull what it needs from other places, like body fat.

When you’re asleep, you aren’t burning as many calories in general as when you’re awake, so the amount of body fat you burn during sleep is pretty low. The same goes for exercising while in a fasted state: the more calories you burn without recently eaten food floating around, the more likely you are to produce energy using stored body fat.

The entire idea works because of a little thing called insulin, which is a hormone that helps you use the food you process the food you eat efficiently. Your body is most sensitive to insulin while in a fasted state, because it’s really not doing much at that point. When you exercise fasted, this sensitivity increases even more, because your body is prepping to store the next bit of food energy it gets as quickly and efficiently as possible. Think of your fasted insulin response as being a Mountain Lion, ready to strike at the first bit of Power Bar that gets into your stomach! Since the system is ready to work in the best way possible, it’s much more likely to store food energy in the muscles (for quickest use later) versus storing it as fat.

You may also recognize insulin as being a major factor in Diabetes, especially the development of the Type II variety. Essentially, eating too much and getting too fat causes your insulin response to wig out (totally a scientific term) and you become desensitized to it. This causes your body to process food poorly, especially sugars, and things start breaking down. Seriously, you can lose your feet from having Type-2 Diabetes. It’s completely preventable with healthy eating and exercise.

How do I include Intermittent Fasting in my health & diet plan?

Two main ways: fast for 24 hours every so many days, or increase your daily time spent fasting every day.

With the 24 hour option, you will fast from about 8:00 PM to 8:00 PM the next day. Do this once every 4 days, on a set schedule. This puts all your fasting caloric deficit on one day which can be tough the first few times you try it. Even if you do the daily version below, I recommend doing one 24 hour fast every 3 weeks or so to help “calibrate” your hunger responses.

With the daily option, you fast for 16-20 hours every day, leaving only a 4-8 hour window for meal consumption. This spreads out the caloric deficit day by day, so you don’t have any one day of more extreme deficit than others. In my opinion, it is easier to do it this way because your body is being asked to adapt to a smaller change than with regular 24 hour fasts.

How can Intermittent Fasting Benefit me?

Before we talked about how the insulin response works, and a bit about how your body behaves around it. Staying in a fasted state helps your body to use body fat preferentially as an energy sources, which means that the longer you fast in a healthy way (see below) the more energy will pull from stored fat. Add a workout while fasted, and this is exacerbated to burn even more body fat than while sedentary. The second benefit is that fasting prepares your insulin response to pounce (remember, it’s a Mountain Lion waiting to strike!) on the energy you feed it after your fasting period/workout, so it stores that energy very efficiently. Even though your first meal will likely be bigger than on non-fasting days, the calories are less likely to be used to create body fat.

For most people that would be enough, but as the guys on infomercials say: But wait, there’s more!

Your body increases the production of Growth Hormone while you’re in a fasting state, which is responsible for helping you build new tissues (especially in kids). In adults, GH is going to help you rebuild the muscles after a hard workout, which pulls resources from food you eat and internal storage. Extending your fast gives the body more GH to use for muscle building, and since your meals are being stored in the best way possible, the energy you take in is even more likely to be used to build up those sexy, rippling calf muscles!

IF also teaches you about your body, which is always a good thing. Hunger can come from a lot of sources (anxiety, pain, fatigue, etc) and IF will help you differentiate between hunger that is brought on by Emotion, Mind, or Body. Body Hunger is the feeling you get when your body is legitimately running low on fuel; it is “real” hunger. Emotional Hunger, also known as stress eating, is almost always brought on by negative emotions as a way to cope with your feelings. Mental Hunger is the mindset of eating on a specific schedule, so that you think you’re hungry based on timing, rather than based on physical needs.

What are the drawbacks to Intermittent Fasting?

I’ve taken myself through prolonged periods of IF several times, usually lasting between 3 weeks and 2 months depending on my goals at the time. Each time I experienced very few negatives about the method. I did notice a pattern that emerged during the first 7-10 days when I began a fasting plan. These effects actually reduced each time I started a new fasting plan, because my brain was better wired to deal with it after some practice. You’ll hit the same point, as well.

Hunger: The mind gets accustomed to things and forms habits, with eating being no different. You get into a timeline of when to eat, so you trick yourself into thinking you’re hungry when, physically, you’re not. Back in the day (like 10,000 years back) you didn’t see cavemen planning out their 6-meal day using the sun’s position in the sky. They ate when they could, and functioned just fine otherwise. Stick to your eating window and you’ll acclimate quickly.

Grumpiness: Back to the brain again! You’ve convinced yourself it’s time to eat every 3 hours, and when you don’t your body starts sending false hunger signals all over the place. Hunger and a feeling of no longer being “on schedule” (humans really don’t like change) makes you feel grumpy and “off” for the first week or so. Or as the kids say, “you get hangry”. It’ll pass.

Low Energy: Some people report low energy during their fasting period as their body adjusts to the new eating routine. You may need to tone down your workouts during this period so you get used to using stored energy instead of food energy while exercising. Again, this usually passes in the first 7-10 days.

How does Intermittent Fasting relate to Starvation Mode?

It really doesn’t. Your body doesn’t start seeing issues from being underfed for about 80 hours, and IF is small-scale fasting for 16-24 hours at a time. You never enter a starvation state and thus IF is not dangerous from that perspective.


And that’s it! If you have any questions, you can email chris [at] crossfitcatonsville [dot] com and I’ll be happy to help!