Tyler Robbins Fitness

B.Sc. Biochemistry, Certified Strength and Conditioning Specialist (CSCS), Certified CrossFit Trainer (CCFT/CF-L3), USA Weightlifting Level 1

Filtering by Tag: glycogen

Fasted Training for Greater Fat Loss?

I actually receive this question from clients quite often, but someone asked me about it again the other morning which inspired me to write about it. The question was, and this goes along with conventional "broscience," is fat burning more effective if you workout fasted?

It is common for individuals to workout first thing in the morning, which many end up doing in a fasted state (haven't eaten anything prior to exercising). Let me start off by saying that I commonly workout in a fasted state, and in fact, have done so for many years. Having said that, I have recently changed my daily routine based on my work schedule so my workouts tend to get pushed to later in the day now. This gives me ample opportunity to eat prior to working out, and although what I am about to say is based off of relatively short period of time and is anecdotal, I have felt like my strength and performance has been much better, but we can discuss more of that later.

Anyways, so the training when fasted theory goes something like this. If you are training fasted, then that means that your circulating blood sugar is low, priming your body to be more conducive to fat metabolism. This is a theory, however, and doesn't quite play out as simply as you would think. To discuss exactly what is going on here, let's break this down into 2 topics of interest.

1. Your body is never entirely using one source of energy over another.

Source: http://ausfit.net.au/understanding-your-body-energy-systems/

Source: http://ausfit.net.au/understanding-your-body-energy-systems/

So you have three energy systems in your body: the Phosphagen System, the Glycolytic System, and the Oxidative System. Without nerding out too far, the Phophagen System produces a lot of power, but can only last for a few seconds (think 3 or less repetitions of something heavy or a short sprint). The Glycolytic System can produce a little less power but can last a bit longer (higher rep resistance training or a longer run, up to about 2 minutes). The Oxidative System cannot generate a lot of force, but is much more lasting in nature (less intense activity such as walking, etc.). The Oxidative System is just that, oxygen-based, so that the amount of breathing you do keeps up with the energy demands of your activity. Oxygen, along with fat, produces energy in the Oxidative System. Your breathing may increase a bit during a brisk walk, for example, but you are never pushed to a point of exhaustion.

During regular, every day activity, our bodies are constantly transitioning between the three energy systems. Walking, talking, general daily activities tend to keep us in our Oxidative state. If we bend down to pick up something heavy, suddenly we transition to either the Glycolytic or Phosphagen system for that quick burst of energy. However, throughout the day, our bodies are constantly metabolizing energy from all 3 energy systems in some ratio depending on the activity.

So how does this change based on whether or not we exercise in a fasted state or not? It doesn't really. Our bodies are great at storing and utilizing energy based on our needs and demands. It doesn't matter when your last meal was, if you need a quick surge of energy to pick up something heavy then you have stored energy for that.

Sure, activity at low intensities when in a fasted state may illicit a greater promotion of fat oxidation, but I would like to think that most people now realize that training in a specific heart rate zone to maximize one energy system over the other is far less beneficial (for overall body composition and health) than exercising intensely.

Not only that, but research tells us that when you are in a fasted state, your body may increase adipose tissue breakdown in order to increase blood triglyceride levels, but the production far outweighs the demand. In other words, the Oxidative System is slow moving and only produces energy at a certain pace - a slow pace at that! So even if you're in a fasted state and your body is increasing blood triglyceride levels, that doesn't mean that those increased levels in the blood are going anywhere. In fact, once you're done exercising, they get shuttled back into your fat cells.

Also keep this in mind: the more carbohydrates you burn during a workout, the more fat you will burn after the workout is over.

Neither the Phosphagen or Glycolytic system require oxygen for their immediate energy output but the Glycolytic System does utilize oxygen in order to replenish spent energy stores. If oxygen demand is not met through respiration during exercise, our bodies go into a state called EPOC, or Excess Post-Exercise Oxygen Consumption. This is oftentimes also called the "afterburn" because calories are still being used to replenish spent energy stores through respiration. This is also why you are still breathing heavy long after an intense workout session.

So let's sum this up.

Low-intensity exercise primarily uses aerobic metabolism (fat oxidation) to generate enough energy for the activity demand. Going for a brisk walk, for example. There may even be some truth to the body metabolizing a higher ratio of fat oxidation when fasted, however this is such a relatively small amount of calories burned compared to much higher intensity exercise.

Performing high intensity exercise will favour more of a carbohydrate-burning metabolism, which sort of defeats the purpose of training fasted. The amount of EPOC you can create for yourself, or in other words, the more intense your workout is, therefore causing a substantial "afterburn" will yield greater calorie burn and fat oxidation.

On top of all of that, research shows that training in a glycogen-depleted state causes the body to burn far more tissue proteins for energy rather than stored energy sources. Muscle protein can account for nearly twice the amount of calories burned in a fasted state versus that of a fed state. In other words, eat before you workout, but train hard!

2. Who really cares how many calories you burn during a workout anyways?

There is a flip side to this coin, however.

I try and remind clients about this on a consistent basis. Keep this thought in your head from now on and it will save you a lot of time and aggravation: Exercise is for your brain and your body. Sure, it burns calories, but you are doing it to keep your machine (your body) running at optimal levels. Body composition is largely controlled by the diet that you eat and the overall net balance of calories in versus calories out.

Doing an hour of light exercise to attempt to stay in your "fat burning zone" will burn such a minuscule amount of calories (in the grand scheme of things) that there really isn't any point in even counting them. Similarly, the amount of calories you may or may not be burning in a fasted state is negligible.

There should be two main factors that your training should focus on if you wish to optimize the amount of adipose tissue you wish to eliminate. First, make sure you are including enough resistance training to work as much muscle during your training sessions as possible. Compound movements involving our primary movers and joints are great for this. Compound movements include such things as squats, deadlifts, presses, rows, etc.

Secondly, your training should be intense. As mentioned above, if you're training intensely, the net amount of calories burned from the exercise itself, followed by the burn long after your workout is over, is far more beneficial from a calorie burning and hormonal response standpoint than trying to target fat loss specifically at a lower heart rate.

Between carrying around more lean mass (muscle), and exercising intensely, your body will be primed to have a much higher resting or basal metabolic rate to maximize your calories burned on a day to day basis.

Does muscle burn fat?

Well, sort of.  Technically muscles burn calories, but it is complicated...

To be honest, I see fitness enthusiasts and Beachbody Coaches using this phrase all the time. Note, there is a vast  difference between a fitness enthusiast and a fitness professional, so be careful what knowledge you are gaining from every individual.

Anyways, saying "muscle burns fat" is like saying "my car burns oxygen". Both are correct statements, but they can be misleading. 

Body fat, also known as adipose tissue serves many functions in the human body. Insulation and energy are its primary functions. To be honest, the body doesn't really like, or want to carry around more weight than it has to, but because our bodies have evolved to also not want to waste or lose too much energy, you end up storing a lot of your extra calories away when you over eat. 

To be honest, muscles' energy 'currency' of choice is something called glycogen. Glycogen is a readily-available energy source stored in the muscle cells as well as the liver. When you perform high-intensity muscle contractions, such as resistance training, your muscles are using glycogen. 

Adipose tissue is more of a slow-burning fuel source because oxygen has to be present during the metabolic process in order for it to be a viable and useful energy source. For example, when you are out for a leisurely walk, your breathing and heart rate are more than capable of keeping up with your cells' oxygen demands, so your primary fuel source is usually adipose.

Having said that, a leisurely walk doesn't really require a whole lot of caloric expenditure, so intense exercise is definitely the way to go if you are trying to maintain a healthy body weight. So how does muscle burn fat exactly? 

Well, as I said before, muscle actually burns glycogen in intense circumstances. It is a quick and fast-burning energy source. But, when intense exercise is over, your body goes into a state known as EPOC (excess post-exercise oxygen consumption) . Think of a sprinter like Usain Bolt. During his 9 seconds of sprinting, he, along with his competitors are probably either holding their breath, or breathing at a pretty normal rate. This is because the body is using anaerobic means to fuel its muscles. Once the race is over, however, their bodies go into EPOC mode. During the post-race interviews, that is when you see them huffing and puffing as they try and replenish those used energy stores.

That  is when adipose tissue is used as fuel by your muscles.

So what advantages can we learn from all of this? 

First of all, the fitter you become, aka, the more efficient your body is at utilizing stored energy reserves, the more effective it will become at using stored adipose as a primary energy source.

Secondly, even though your muscles don't directly burn adipose, intensity is definitely the name of the game. An intense, efficient, and effective resistance workout is the best way to go to maintain a healthy weight, as EPOC, as well as micro trauma in the muscle fibers can cause a spike in metabolism and calorie burn for up to 72 hours following a workout.

A Diet I Can Count On!

*DISCLAIMER*  - The intention of this blog is not to tell any of you how to live your life or to preach about a diet plan that everyone should follow. I have received several requests about my "new" diet, so I am detailing what I have been doing. This diet plan is not for everyone. Diet plans should be tailored to each individual's needs similar to how different athletes train for different sporting events. No one diet is right for anyone, so you should find a diet plan that works for you, makes you feel good, and is sustainable. Any questions beyond this blog can be commented below, or you can e-mail me and I will either respond to your questions directly or will bring them up in a future blog.

june 16 2013.jpg

I will first get right into the nitty-gritty of how I have been eating lately, then I will delve further into the "whys" below. My days are pretty standard, they are pretty much based around whether or not I am using resistance training or not (explanation below). 

Resistance Training Days 

5am - Wakeup, have coffee, no sugar, small amount of milk
5:30am-6:30/7am - Workout (fasted state)
Post-Workout - Chocolate milk with Creatine
Breakfast (usually anywhere between 730-9am - 3 scrambled eggs, Banana
Lunch (usually around noon, varies greatly day by day what I eat. At this point, not entirely relevant what  I eat, I can explain later)
Afternoon Snack (3-4pm) - Double Protein Shake (52g protein) with Apple/other fruit
Dinner (5-6pm) - Like lunch, I vary greatly with what I eat
Snack (7pm) - Peanut Butter - usually 3-4 tablespoons (I LOVE Peanut Butter)
Pre-Bed Snack (9:30pm) - Cottage Cheese mixed with vanilla yogurt

Non-Resistance Training Days 

5am - Wakeup, have coffee, no sugar, small amount of milk
5:30am-6:30/7am - Workout (fasted state)
Post-Workout - Fast
Breakfast - skip
Lunch (usually around 12:30-1pm on these days)
 Afternoon Snack (3-4pm) - Double Protein Shake (52g protein) with Apple/other fruit
Dinner (5-6pm) - Like lunch, I vary greatly with what I eat
Snack (7pm) - Peanut Butter - usually 3-4 tablespoons (I LOVE Peanut Butter)
Pre-Bed Snack (9:30pm) - Cottage Cheese mixed with vanilla yogurt
The main difference here? Unless I am doing a very tough resistance workout, I stay in a fasted state for around 14-15 hours (9:30pm the previous night to lunch that next day). To be honest, this plan can work for whatever your goals are (bulking, cutting, losing weight, etc.) as long as you still stick to your macronutrient goals.

Here is why this plan works for me 

I have been "intermittent fasting" for nearly my whole life (at different times), I just didn't realize that it  had a name. I have never really been a fan of breakfast. I don't really like the options I have been given, such as cereal, eggs and bacon, etc. Oftentimes as a teenager, I would get up and be off to do something  rather than sit down to start my day with a hearty, well-rounded breakfast.

Well, why is it that everyone keeps saying that breakfast is the most important meal of the day? Well, there have been many studies showing that folks who eat a full breakfast can lose weight because the theory is that those who have a nice, full breakfast take in fewer calories throughout the rest of the day. The question is, if so many people are eating breakfast, then why are so many of them also dealing with weight issues?

Well, one explanation to that could be the fact that what  they are eating for breakfast is the problem, not necessarily eating breakfast in general. I get that. I am not here to put all of the blame on breakfast, I just choose to skip it (when I choose to fast) because it works best for me.

On the days that I fast, I am training my body just as I would if I was to train for a marathon. If I wanted to train for a marathon, I would do training runs. Intermittent fasting allows me to train my body to better utilize fat as an energy source. By not eating until lunch, I am forcing my body to utilize fat stores throughout the morning as an energy source.

 But what about your workouts, aren't you catabolizing your muscles?

Short answer, no! Your body is an extremely efficient machine. So much so, that it knows how to store little pockets of energy throughout for times of need. For slower, long-duration events, you have stores of body fat (adipose tissue). For periods of fast, powerful, or strong movements (lifting weights, circuit training, etc.) your body stores sugar in a form called "glycogen" .

There is sufficient stores of glycogen for your body to exert high amounts of energy for well over an hour of hard exercise. If, however, I was to be training for longer periods of time (long endurance run for example) then I would make sure I would take some sort of food with me so that I don't "hit the wall". 

Humans have evolved over time to essentially always have a even just a little bit of glycogen stored in our muscles. Even if you are working extremely hard, you are probably not going to use all  of that stored glycogen. This is due to our early ancestors and their need to flee predators.

How do you go without food for that  long? 

Well, intermittent fasting (IF) is not the easiest of things to practice, especially if you aren't use to it. As I said, I have been dabbling with IF for years, just not realizing that that  was the name for it!

I have always been one to eat before bed. When I was younger, I struggled to keep weight on, so I developed a habit of eating every  night before bed. My pre-bed snacking has not always been the healthiest, but regardless, I ate before bed.

If one was to aim for a 15-16 hour window of fasting, for me personally, before bed would not fit into that window, so naturally, I like to continue my fast right after I wake. It is not all bad either, as I drink coffee (essentially zero-calorie) and water throughout the morning to help quench my hunger pangs! Practice definitely helps though.

If you can't make it all  morning on your first couple of tries fasting, don't sweat it. Maybe aim to skip breakfast, then have a small snack a few hours later. Over time, you will become better and better at resisting the urge to eat, and can hold out for longer and longer. I personally find that 15-16 hours is a perfect window for me, but some day I may try to hold out for even longer .

IF Pros 

Here are a few things that I really enjoy about fasting: 

  After a few months of IF

 After a few months of IF

1. I actually find I have more  energy and mental clarity throughout the morning! How many of you sit down to a big meal and afterwards feel slow, groggy, sluggish, bloated, etc. show of hands...exactly! Despite what you may think, going without food is good for you, and as I explained earlier, can make your body more efficient at using the energy stores that it has. I also find that for whatever reason, right around the 13 hour mark (approximately) I hit this point of mental clarity. Like a switch suddenly gets flipped and I can think so clearly!

2. I prove to myself how much self control I have every day I choose to fast. Whether I am making my son some breakfast, or I am out of the house and smell a delicious restaurant as I pass by, I keep reminding myself that I am not eating for another 2, 3, or even 4 hours. It is incredibly exhilarating to win those mental battles and just know that you are in complete control of what you eat. This can also carry over to those days when people around you are eating junk, and all you have is a piece of salmon and some steamed vegetables.

3. Related to #2, when you do eventually get to eat, man oh man is it delicious! I am not a big fan of eggs, I will fully admit. I have never been a big fan, but I have grown to appreciate their nutritional importance. Well, on those days when I am fasting and I decide to have some scrambled eggs with peppers for lunch (actually my "break"fast) it is like the tastiest thing I have ever eaten! 

4. Your eating window has just shrunk! Probably one of the biggest pros for many of you out there! Let's say you are trying to lose weight, so you have allotted yourself 2000 calories/day. Now, let's say you eat breakfast (first meal of the day) at 7am, and dinner (last meal of the day) at 6pm. That is an 11-hour window to take in 2000 calories. Now, instead, imagine you skip breakfast, and don't start eating until 1pm (first meal). You now have a 5-hour window to eat 2000 calories. That means larger meals/snacks, making you feel more full (satiated). All of this nonsense about eating 6 small meals throughout the day? I don't like it and don't buy it for a second. If and when I eat, I like to EAT! When I have some small, little, piddly snack, I just end up more  hungry than I was before!

Cons with IF 

1. This takes time, patience, and a true understanding of your body.  Don't expect to be able to just pick up and start skipping breakfast if you have been eating breakfast your entire life. Your body is used to that fuel to start your day.

2. Don't let your brain make poor decisions. It is very common for people to come out of a fast and grab whatever is closest to them to eat, or in a lot of cases, the most convenient. When fasting, your body's blood sugar levels drop as your body uses up free-floating sugar in your bloodstream. This can cause your brain to trick you into thinking you are hungry for sugar. Not necessarily the case. You are probably hungry, yes, but you are hungry in general, and grabbing a glazed doughnut is not the answer. When I come out of a fast and eat lunch, I usually have some scrambled eggs, sometimes with some chopped peppers thrown in, and then my Shakeology . Easy on the stomach and chalk-full of the macro and micro nutrients that my body is craving!

3. People will think you're crazy. Trust me. "But breakfast is the most important meal of the day!" Why? "Because that's what they  say!" Yeah, well, they  also say that "fat free" is healthy for you, and if you have been following my blog long enough, you should know that that is certainly not the case. Remember, there are a lot of "normal" people out there, doing "normal" things, leading "normal" lives, the majority of whom are unhealthy, out of shape, and overweight. So tell me, what exactly is "normal" about that?

I will close this blog with how I started. Intermittent Fasting is not for everyone. I am not trying to convince any of you to make such a (drastic) lifestyle change, all I am doing is sharing my experience with IF and how it has helped me. If you have any questions, please do not hesitate to e-mail me, or comment below!