Last time we spoke about how carbohydrates create energy for athletes. If you have not read that article you may be lost so please read it before this one. CARB METABOLISM ARTICLE .
This section will focus on the complex processes of how a fatty acid is broken down, transported and used for energy in the cell. Again I will give you the main ideas rather than complicate the situation with big fancy biological names.
First of all, fat cells, known as adipocytes and lipids, are large vacuoles of space and inside this space are triglycerides. This is a word most people have heard before but for many the actual meaning of the word is hazy. “Tri”- meaning three fatty acid chains of molecules attached to a glycerol back bone. These fatty acids are broken off the glycerol back bone and transported to where ever it needs to go. That is basically it. Let’s look at this incredible process more closely.
Assuming our host is doing slow exercise or is in a fasted state, fat will be the main nutrient for producing energy. This is because glucose levels in the blood are low due to one of the above reasons unless you have a medical situation such as diabetes. Once the blood glucose levels are low then the body senses this with receptors in the arteries that literally are stuck in the walls and sends a signal to the brain saying “Hey man, we need more energy and we are out of glucose” . You may ask why do we not use the glucose from glycogen as discussed in our last article HERE. We already have. The first signal of the brain is to use up glycogen stores in the muscle or liver as we get the most energy from Carbohydrates. When these are out then the body has to go to its secondary nutrient, ie. fat. The hormone Epinephrine is sent from the medulla of the Adrenal Glands, located on top of the kidneys. Some research shows that Glucagon can be used to activate this process as well because it is the starvation hormone. It is activated when the body does not have enough glucose. Other research shows that this is not the case and that inhibiting insulin, a hormone that takes up glucose out of the cell, is the source of this activation.
When epinephrine binds to the outside of the cell it causes a signalling cascade which activates many different proteins along the way each passing a signal to the, eventually affected target. A signalling cascade is a fancy word for a many step process that includes rearranging and creating different molecules from current ones. In this case our end target is triglyceride. First epinephrine binds to Beta-Adrenergic Receptor, a protein imbedded into the phospholipid bilayer, also known as the cell membrane. This activates G protein which in turn activates Adenylate Cyclase. After this step ATP is added to the process and bonds are broken to release energy in order to keep the reaction moving forward. ATP turns into Cyclic AMP, which is a signalling molecule. This molecule activates Protein Kinase A. Here, another ATP is broken, but only one this time, to create a bit of energy and forming a molecule of ADP which is recycled for later use. Using this last ATP activates the Hormone Sensative Lipase which is the hormone that cuts off two of the fatty acids. Monoacylglycerol Lipase comes and finishes the job by cleaving off the last fatty acid chain. YAY, now we have 3 single fatty acids floating around and a glycerol back bone. A whole lots of mumbo jumbo to really only say that molecules are told to break off the fatty acid chains from the glycerol backbone.
So what now? Well glycerol can have two fates depending on the situation. If the body is in a need for glycolysis (Energy) such as during exercise, as mentioned above, the glycerol back bone can be converted into Dihydroxyacitone Phosphate. (DHAP) This is where you guys suffer for not having me list off every molecule in glycolysis. DHAP is the 5thstep of glycolysis meaning that if we were to add more of these DHAP molecules then more substrates are available to fuel glycolysis WITHOUT GLUCOSE!!
The glycerol can also be used to create more triglycerides if need be. This may occur when a work out is finishing. The body does not need any more energy and maybe it broke down a few too many TGI’s and now has nowhere to put them. Time to recycle. This process takes a few more steps but inevitable ends up with a molecule of TGI.
So we have dealt with the glycerol and still have the fatty acids to deal with. The FA’s (fatty acids (Broken off branches from Glycerol)) go to the cell membrane and diffuse through the membrane and attach to Albumin. Albumin is a carrier protein that attaches FA’s and transports them via the blood stream to a cell where they can be put into the mitochondria. The mitochondria is the energy factory of the cell. Albumin is found in eggs as the white portion we see when we cook them. Intracellular carrier proteins grab the fatty acids and transport them into the cell once they reached the cell. Just before the fatty acids go into the mitochondria each fatty acid has to be “Activated” . This is done by adding a Coenzyme A onto carboxylic acid group. This is the side of the fatty acid that was attached to the glycerol backbone and consists of two oxygen’s and a hydrogen.
I guess we should take a minute a describe a fatty acid. A fatty acid is known as a hydrocarbon chain. It consists of a carbon back bone with two hydrogen’s attached to each carbon. This fatty acid is always moving around slightly and not fixed in an immoveable structure. This is important because it allows the cell membrane ( phospholipid bilayer) to move around and helps the cell function. It is like putting a human in a straight jacket. They do not have very good function and there is no way a mental patient deserving of this special treatment can be in the Olympics. We want all of our cells to be in the Olympics and to work at their greatest capacity. This is where bonds come into play. A saturated fatty acid chain is straight with single bonds on every carbon. It is bad for the cell to be made of too many of these for the above reason, not enough freedom to move. The same fatty acid can have one or more double bonds and this causes the fatty acid to change shape and twist a bit and actually makes the fatty acid more moveable on the triglyceride and the cell membrane. The more moveable the fatty is, potentially better it is. These are known as Monounsaturated fatty acids or polyunsaturated fatty acids. Trans-fats are a derivative of a polyunsaturated fatty acid where the double bond simply faces the opposite direction. This in a natural form is good for us but when influenced by heat or by pressure then it turns out bad for us and that is where the “trans fat” dogma came from.
Companies do not naturally make food because chemicals and heat and pressure and other processes change the molecules for the worse. Omega 3 and 6 basically is a naming technique used by scientists to differentiate different fatty acids. “3” and 6” simply determine what carbon the first double bond is on. Omega 3 is an “Essential” fatty acid meaning it has to be ingested to get into our system from the outside and the body does not have the ability to making it interiorly. Too many Omega 6 fatty acids are said to compete for the same rate limiting enzymes as omega 3’s and for this reason are said to be bad in large amounts. Im sure most of this went over your head but the reality is that we need fats in our system; in appropriate amounts they are healthy and actually required; and Omega 1/2/3/4…25/26, is just a way to label the structure of the type of fat you are ingesting. The only difference in types of fats is where double bonds are located which changes the shape which changes the action in the body. Phewww glad that is over.
Back to fat metabolism. We were discussing how to activate a fatty acid chain before it gets into the energy factory. While activating the fatty acid a “thiol” group, simply a sulfur molecule, is added to the fatty acid chain. This thiol group has a lot of energy and can be broken like an ATP to fuel reactions. ATP is used to create this “activated” state of the fatty acid but that is a necessary consequence. Now the fatty acid is ready to go into the mitochondria. It diffuses through the outer membrane of the mitochondria but it has to be transported into the inner membrane with a carrier called Carnitine. Carnitine is just a protein that acts like a transit bus. Fatty acids hop on the bus and get transported to the mitochondria. Again, simply put, there are different layers of the mitochondria just like the human skin has several layers; 7 if i remember correctly. The FA attaches to this molecule and rides in into the inner membrane of the mitochondria. In the process of attaching to the Carnitine molecule the Coenzyme A is dropped and recycled.
Honestly let’s take a minute to marvel in the amazingness of the human body. How amazing is it that our body knows this and can regulate all these different molecules all day everyday. It would be like one company controlling the entire world. A single board of directors that regulates how every city works, how every citizen can be made to maximize their value and how to grow the world. The human body is magical and just leaves me bewildered how it came to be. But any who… The below picture tries to simplify metabolism into very easy major stages.
Now it is time for Beta Oxidation, once the fatty acid attached to the Carnitine travels into the inner membrane of the mitochondria. Basically, Beta Oxidation is a few step process where fatty acid chains sometimes 30 molecules long are shortened by two carbon molecules. This forms Acetyl CoA. If you read the last article then you would know this is a substrate for the Kreb cycle which powers glucose metabolism. It is interesting how each process can aid other processes that seeming have nothing to do with each other. In addition to Acetyl CoA; NAD and FAD is produced in these few reactions which can go into the ETC, which we also discussed last article HERE. So with all these Acetyl CoA’s we are producing a lot of energy from fat. 1 gram of Glucose molecule creates roughly 4Kcal of Energy. 1 gram of fat creates 9 Kcal. So why not just use fat? Fat makes more energy but as you can see there are more steps and it takes longer. Thats it. Glycolysis that breaks down glucose almost instantly for a quick 30 second sprint or take the time to break down fat for several hours of energy like a marathon? Well we know that Gymnastics and Trampoline use Glycolysis as it is a quick burst of energy. I think it is important to know why fat is not the prime energy source of acrobatic elements. I have heard coaches say that athletes should stock up on fats for training purposes. Sorry, it won’t help. You need to train the quick energy systems for the acrobatic world.
“Well Greg, I train 5 hours a day, so it is like a marathon, so I need fat metabolism”.
Yes and No. You are not doing a low intensity constant duration. You are doing high power intervals for 5 hours. One factor that should be considered however is recovery time. This will allow the athlete to get in more full powered reps into 5 hours. This is done at the start of the year to create an “anaerobic base” as the kinesiologists call it. This means that your body, no matter how power based it is, has a fat metabolism base that determines how exhausted you are after a power interval floor routine that lasts 45 seconds.
Fat metabolism will NOT help you tumble better with more power, but it will help you get in more reps which is a big part of training obviously. So even though I say that fat metabolism is not the goal for training, it is a necessary side dish to any athletes main course.
If the Acetyl CoA’s do not go into the Kreb Cycle they will be converted into ketones in the liver. This happens in small amounts normally and the keytones are reconverted into acetyl CoA’s to be put back into different processes such as Kreb Cycle. In times of starvation keytones are used as an energy source in the brain and can cause a lot of harmful side effects. Keytones are BAD! I know there is a lot of hype about Ketogenic diets which just basically means you starve your body so it breaks down fat. If you ask me you can just hit the gym 3 times a week, eat 1,500 Kcal a day and you will be ok. 3,500 Kcal = 1 lbs of fat. So if you are 10lbs overweight it just means you have 35,000 more calories then your body can use so it stores it. The lengthy process of this fat metabolism shows you why it is hard for anyone to lose weight. They say it is harder to lose weight then to quit smoking.
I know that this article does not directly help athletes who are acrobatically inclined but to understand the very basics of how energy is created and used in the body is a necessity for anyone who wishes to use their body at max capacity.
Take home points? Do not worry about fat’s so much but understand that without a good fat metabolism base you may feel winded at training. Training the fat metabolism aspect of your body won’t make you jump higher or hold your cross longer but it will help you have a more productive training.
I remember not thinking about it as a kid but had the best cardio in the group. Everyone else would be tired after a few trampoline routines and I was jumping around between resting and routines training other things as I had the energy. I think it made a huge difference in my overall growth in the sport as I could simply get more done in the same amount of time. I had the highest V02 and the top lactic acid recovery rate at sky riders when the testers came and measured our blood.
I think having that much energy and ability to recover also mentally made me accomplish more because I was not tired and panting after every turn. I was eager and mentally ready for big trick as well. Overall I really encourage a strong aerobic base as well as lots of power during the bulk of training.
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