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Overview Of Intermittent Fasting: Part Two

In part two on this series on the subject of intermittent fasting we’ll look at the physiology behind how the strategies work along with comparing some of the most popular IF programs. Refer back to part one if you need to get up to speed on what intermittent fasting is.

Bear with me for a minute as we’re going to get into some technical stuff with the physiology, but I’ll do my best to simplify things. It’s important we cover this though so you have a complete understanding of how intermittent fasting impacts your body.

More after the jump…

What happens to my body when I do intermittent fasting?

Ok, so we know from part one of this series that intermittent fasting is in essence extending the period of time between feedings. The length of time of the fast is typically 16-24 hours, sometimes less. It’s important to note that not all intermittent fasting strategies have you eating NOTHING during the fasting phase.

As you’ll see later some IF plans incorporate easily to assimilate nutrients from things like fruits, vegetables, green juices, etc.

The question is what’s the main benefit of going the extended time between meals?

The answer lies in the natural cycles of your body.

This is where things should start really making sense and the light bulb will go on. You’ll be like “ah, yeah now I get it.”

I want to talk about two different phases or cycles of your body. Every day each one of us goes through “catabolic” and “anabolic” phases. In simple terms, catabolic refers to “breaking down” and anabolic refers to “building up.”

During the day when you’re working, running around doing errands, exercising, or whatever, you’re in a catabolic state. You’re breaking down substrates and nutrients into smaller units for the production of energy along with a host of other metabolic functions.

It’s your sympathetic nervous system that’s at work here. The more stressed you are, the  more caffeine you drink, etc, the harder your sympathetic nervous system works. Obviously, too much stimulation and bad things start to happen. The adrenal glands become fatigued from constantly pumping out catecholamines like epinephrine and norepinephrine.

Cortisol levels shoot through the roof and this triggers changes throughout the body. Next thing you know you’re constantly tired, fatigue, struggling with your weight, and feel like a zombie trying to get through the day.

The sympathetic nervous system works to provide energy when we need it in short bursts as part of a primal flight-or-flight response. It’s not supposed to be driving the car all the time. The problem with a lot of folks is they’re constantly under stressors which over-stimulate the sympathetic nervous system.

When stress is already on high, the body has to work even harder when demands for digestion are constantly in play. Consuming processed food and drink that is high in sugar, toxins, an unnatural ingredients calls upon the organs and glands of the body to work extra hard in processing and elimination.

This is especially true for the liver which is in essence the main filter for the human body. The long and short of this is digesting food and drink is a catabolic process. The harder your body has to work to do this, the more your sympathetic nervous system is at play.

Eat a big meal and you get sleepy shortly after, now you know why. Your body is sapping all your energy for digestive functions. This is energy that could be used for mental and physical activity.

On the flip side, it’s your parasympathetic nervous system at play during the night when you’re in an anabolic state. This is where you’re building back up, repairing, and rejuvenating. It’s like the ying and yang, you’ve got time when you’re catabolic and time when you’re anabolic.

The key here is there needs to be balance. Spend too much time in a catabolic state, being overly stressed, following a poor diet, not getting enough sleep, etc, and your body starts breaking down.

Instead of breaking down nutrients for energy, you’re breaking down at the cellular level, hormonal levels drop, things basically get out of whack.

Ok, hopefully now you’ve got the whole catabolic, anabolic, sympathetic, and parasympathetic nervous system concepts.

The idea behind extending the normal fasting state when you’re sleeping (in an anabolic state with the parasympathetic nervous system driving) is in essence to give your body a break.

Basically what you’re doing is extending the detoxification and cleansing phase of your body. Remember with digestion we’ve got the breakdown of food into smaller particles, assimilation into the blood stream, utilization, and finally elimination.

The body has a natural flow to things as we’re typically catabolic during the day with the breakdown and utilization of energy. At night you’re working on the elimination phase of digestion. This extends into the morning when you awaken. When things are working properly you should be going to the bathroom first thing in the morning.

During a fasting state, the body continues to detoxify and cleanse while you’re able to remain under the direction of the parasympathetic nervous system. The gastrointestinal tract and organs are given a break and a ton of energy is freed up to be used elsewhere.

This is why those who practice IF strategies will tell you that mental clarity and focus often goes up during the fasting state. When you’re not constantly bogging down your digestive tract, good things start to happen.

Without the readily available sugars, fats, and other substrates from food for energy, the body can tap into reserves. This is not a bad thing as humans have evolved this way. Stored carbohydrate (glycogen) can be used for energy, body fat stores can be used for energy, even protein can be broken down to produce glucose for fuel.

The bottom line is the human body doesn’t need food in pulse feedings 24-7 to function. It has the ability to pull upon stored reserves and can function quite well this way. If this wasn’t the case we’d all need to be getting up during the night to eat.

I want you to think about intermittent fasting as not just a way to tap into stored fat, it’s a means of giving your body a break. It’s a way to promote cellular rejuvenation, cleansing, detoxification, and balance.

Think about the difference between loading up on a big breakfast of starchy carbs, proteins, and fats, all needing to be broken down requiring large amounts of energy, compared to perhaps drinking a green juice or eating a bowl of berries for example.

The simple sugars and nutrients in greens, vegetables, and fruits can be easily assimilated and utilized for energy in a blink. The digestive tract isn’t burdened in the least. Your body literally soaks up the vitamins, minerals, and phytonutrients in these foods like a sponge. All the while these nutrients actually assist in the detoxification and cleansing process.

This isn’t to say that a bigger breakfast isn’t sometimes in order. I’m not making a case for everyone to do IF or to consume only fruits and greens for breakfast. I just want you to see the difference and the implications it has on the body.

Intermittent fasting makes sense from a physiological standpoint because it follows the natural cycles of the body. In a lot of ways it enhances these cycles allowing for a balance between sympathetic and parasympathetic nervous system function.

There’s a lot more to cover regarding the hormonal implications of intermittent fasting and breaking of the fast in regards to fat loss, lean muscle development, etc. We’ll dig into more detail in a following segment of this series.

For now, let’s briefly look the differences between some of the more popular intermittent fasting programs.

Comparing a few of the more popular intermittent fasting routines…

I’m going to provide a general overview of some IF variations, but save my critique and recommendations for a later segment.

Alternate Day Fasting (ADF)
(36 hour fast /12 hour feed)

With the Alternate Day Fasting regiment you’d basically eat every other day. For example, on Monday you’d eat within a 12 hour window, say 8AM to 8PM. Then you’d fast overnight and all day/night on Tuesday. You’d eat again on Wednesday within a 12 hour window then repeat the cycle.

Meal Skipping

You’ll find some IF advocates who adhere to Paleo principals and believe we should behave like our evolutionary ancestors, eating their food at random. With random IF strategies you would skip a meal like breakfast or dinner perhaps once or twice a week. The rules are pretty flexible as there’s no real order to this. You would in essence simply extend the time between feedings once or more during the week .

24 Hour Intermittent Fasting
(24 hour fast, 1 or 2 times per week)

On this plan you would use intermittent fasting for 24 hours, once or twice during the week. You pick the 24 hour period in which you want to fast. Could be from breakfast to breakfast, from dinner to dinner, you name it. Once again, the guidelines are pretty flexible. Of course when you’re eating you’ll want to make good choices from whole, natural foods, minimizing processed and refined foods.

(16 hour fast, 8 hour feed)

This routine made popular by IF guru, Martin Berkhan, has you fasting for 16 hours then feeding for 8 hours. There are guidelines and structure to his plan. The diet should be high in protein, should cycle carbohydrates, include fasted training, and incorporate nutrient timing (in essence consuming the bulk of your calories during your post-workout meal).

On this plan you might use intermittent fasting from 9PM until 1PM the following day. Ideally your workout would come right before the end of the fast (although there are modifications for this). On the Leangains plan, you’d consume 10 grams of BCAA’s (branched chain amino acids), before your weight training workout. After training you’d consume 2-3 meals before 9PM, the largest of course coming right after the workout.

Warrior Diet
(16 hour fast / 6-8 hour feed)

The Warrior Diet by Ori Hofmekler is considered by many to be the source of all other intermittent fasting strategies. He was the first, as far as I know, to come out with the ideas of promoting intermittent fasting by sharing a lesson in history with how the ancient Greek and Roman warriors ate.

His book, by the same name, is a great read and I highly recommend it. Regardless of whether or not you elect to use IF strategies, he does a thorough job of explaining the principals and you’ll certainly find food for thought.

With the Warrior Diet you’d fast from dinner until approximately 1PM the following day. One of the differences with his intermittent fasting strategy is the inclusion of some light, easy to assimilate nutrients during what he calls the “undereating phase.”

During the day he recommends light eating of things like fruits, vegetables, greens, and proteins. This includes freshly prepared fruit and green juices, natural yogurt, kefir, whey and milk protein shakes, poached and boiled eggs.

The “overeating” phase as he calls it starts in the evening with dinner and extends until an hour or two before bed. This is where you’ll consume the majority of your calories. Heavier proteins and starches are now included. You ease into the feeding phase with a large garden salad then eat until you’re full from proteins, vegetables, and starches like rice, potatoes, etc.

Renegade Diet
(16 hour fast / 8 hour feed)

The Renegade Diet by Jason Ferruggia is in a lot of ways a twist on the Warrior Diet. Jason draws reference to the Warrior Diet as being instrumental in coming up with his own variation of intermittent fasting. For those of you who aren’t familiar with Jason Ferruggia, he’s one of the sharpest minds out there on strength and conditioning and human performance. Simply put, the man knows his stuff.

The Renegade Diet basically has you fasting from dinner until 1PM the following day, much the same as the Warrior Diet. The difference is with his plan, you’re not eating anything from dinner until 1PM the following day. Morning coffee is permitted but it’s a true fasting state with no food.

There’s more structure here with you ending the fast at approximately 1PM then beginning an “underfeeding” phase eating only easy to digest and assimilate proteins, fats, and non-starchy vegetables (no starch carbs).

Following the 4 hour underfeeding phase you’d enter a 4 hour “feeding” phase where the bulk of your calories would be consumed. This includes heavier proteins and starches. He does have an order in which to follow in regards to what to eat first and there’s certainly structure.

What’s coming next…

I’ll give you my review of the various plans I just listed in one of the final posts on this series. This post is already getting long so I think it’s time to wrap it up for today.

Tomorrow in part three, we’ll look at some of the considerations regarding food choices when ending your fast depending on your individual needs and goals. The strategies change depending on your body type and what you’re trying to accomplish.

In the meantime, once again feel free to leave your comments or questions.

Shane Doll is a certified Charleston personal trainer, fat loss expert, speaker, and founder of Shaping Concepts. With a staff of over 10 certified fitness professionals, Shaping Concepts provides fitness consulting in Charleston with a specialty on weight loss and body transformation. See our success stories from numerous Lowcountry residents then sign up for a no-obligations consultation today.

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Category: Fat Loss.