Tag Archives: energy systems

Fat and Running


Hope you guys have been keeping well. I have not been blogging consistently. WHOOPS! I’ve got a lot on my plate right now and I’m feeling a little overwhelmed (in a good way!)! Please bear with me on this one. Life is getting a little bit more exciting and I hope to be able to share the good news with you guys soon!

If you’ve been following my posts lately, you will notice that I’ve been talking about FUEL and RUNNING.

Just a quick recap:

We talked about carbohydrates, how to maximise our stores (glycogen stores) before a run and how to reduce dependence on these stores during a run!

An important point to note is that carbohydrate stores, both in our liver and muscles, ARE LIMITED.

Thankfully, our bodies have another source of energy – FAT!

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Fat is basically UNLIMITED. You can’t run out of fat. If you do, you’ll die.

From the above statement, you can see why tapping into your fat stores would be an advantage. If you can train your body to increase its reliance on fat stores, you will be a fairly good endurance runner!

Fat is stored in adipose tissue (fat cells) and muscle.


Pinch the side on your tummy and you’d probably be pinching some FAT. Fat cells are found all over the body: abdominal area, buttocks, hips and under the skin. The more we eat, the more fat we store and it becomes our energy reserve.

However, storage fat is not essential for health and too much of it increases the risk of certain diseases.


Fat stored in muscle is known as intramuscular triglycerides. Found throughout skeletal muscles, they are available for immediate use during exercise [1].

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The story is not as straight forward for fat cells (compared to muscle fats). Storage fat needs to be broken down into fatty acids and transported to the muscles to be used for energy.

Free fatty acids (from fat cells) and muscle fat provide energy to fuel your running.

Which fuel you burn (Carbohydrates or Fats) during running depends on the intensity and duration of it (more on that later). However, how much fat you burn depends largely on your genes as well as training and nutrition.

Although genes wear the biggest hat, you can always train your body to burn more fat at higher running intensities.

Fatigue sets in when your body is low on fuel. As mentioned, fat is virtually limitless which makes it a very attractive source of fuel.

So, the question is: How to become a fat burner?

Becoming a FAT BURNER

The answer lies in endurance training. As you know, when you’re running a marathon, you’re running at a submaximal pace. At this intensity, your body uses more fat. Many months of training and running miles logged would mean that you will burn more fats as compared to carbohydrates at the same intensity. When the weight is off muscle glycogen and blood glucose, you delay fatigue. This ultimately translates to better running performance.


As mentioned, for fat to be used as fuel, it must first be broken down into fatty acids, mobilised and transported to the muscles to be burned. Endurance training enhances the capacity of muscles to use fat. It stimulates the production of enzymes that would enhance all the steps required to use fat as fuel [2].

In the presence of oxygen, mitochondria are the factory that produces ATP (body’s energy currency). Endurance training increases the number of mitochondria in a cell which means that you can produce more energy from fat (fats are being ‘burned’ in the mitochondria) [2].

Running puts a certain amount of stress on the body. When you start running, the sympathetic nervous system (fight or flight response) comes into play. The main energy fuel that is used to meet the sudden demand of energy is carbohydrates. Thankfully, humans are highly adaptable and we are able to learn and change to better handle that stress in the future. Training reduces this sympathetic response and puts a greater reliance on fat as fuel [3].


Throwback to when I first started running.

Remember how hard it was when you first started running – your breathing was all over the place, your heart felt like it was going to explode and your limbs had a mind of its own – but you continued anyway? And then a few weeks later you realised that running is the easiest thing in the world. That is because your body adapted to the “stress”.

At the same running speed, a trained individual is a fat burner that relies less on carbohydrates to fuel their running at the same intensity as an untrained individual. IMG_0897

These training adaptations don’t take place overnight. There are no short cuts. You can see how training, hard work and effort are keys to unlocking the lock to becoming a great runner.

But if you happen to have a problem with committing to training, maybe there’s a way out. Ever heard of fat-loading diets? We’ll explore that next!

Till then, keep running! 🙂

Fuel and Running – Part 2 – Maximising Glycogen Stores

As mentioned in the previous post, runners use both carbohydrates and fats during a run.

We won’t be talking about protein because protein is only broken down during extreme cases.58d054bbb9c5b14b3eceef810e7bef0c

The percentage of which fuel a runner uses depends on the INTENSITY of the run (which will be discussed in another post!). For now, we will focus on the FUEL.


We are all familiar with carbs – the rice, the breads, the noodles. The very food group people try to avoid when they want to lose weight (Not all carbs are “bad”. You just have to find what is right for you!).


They are stored in the body as glycogen and broken down to glucose when the body needs it.


There are limits as to how much glycogen you can store in your liver (about 100-200g) and muscle tissues (about 400-500g). It takes about 120 minutes of running to deplete your glycogen stores.

As discussed, low glycogen stores and blood glucose levels have ill effects on running performance which would either require you to slow to a walk or STOP completely.

Maximising Glycogen Stores


In runner’s vocabulary, it’s called CARBO-LOADING. Carbo-loading involves significantly increasing carbohydrate intake a few days prior to a race. There is evidence that higher pre-exercise glycogen levels delay fatigue.


Although there are a few limitations on the studies performed on carbo-loading, it is safe to say that runners will benefit from it prior (final 3 days) to racing or running longer distances (especially when it comes to speed and performance).

When and How Much?

Carbo-loading takes place during taper week, 3 days before the big day (NOT one week).

Some people begin carbo-loading a week before the big event and takes this opportunity to “EAT ALL YOU CAN” (not a good idea unless you plan to ruin your race day performance).


The recommended amount is 8-12g per KG per day.

For me (45KG), that is about 450g of CARBS PER DAY, equivalent to about 40 slices of bread. BREAD MONSTAHHHH! Even if you’re a big eater, it is not easy to consume the recommended amount of carbs.

When I was preparing for SCKLM 2014, I wrote down every food and drink consumed. I had to have a sense of what I was putting into my mouth. I calculated exactly how many grams of carbs (in everything) to make sure that I ate the right amount. Even then, I was always on a mini binge at night because I hadn’t eaten enough. Runners can opt to drink (sports drinks, milk etc) their carbs if eating is too much to handle.

I did not practice carbo-loading before race day but I recommend that you try at least once to get the feel of it.

Does it Work?

In my experience, carbo-loading WORKS (for a marathon)! I did not hit the wall when I ran my first marathon. Training and carbo-loading done right? Probably. If anybody is interested, I can share what I had during the carbo-loading phase.


You often hear people “carbo-loading” for every race regardless of the distance. Is it necessary? Carbo-loading is unlikely to be effective for events below 120 minutes. You would have sufficient energy to fuel your run and the excess weight gained during the carbo-loading phase will in fact SLOW you down.

Although carbo-loading during the final 3 days leading up to race day is needed to top off glycogen stores, how you replenish your stores on a day to day basis is probably more important. What you eat DURING training will allow you to recover and ensures that you reap the benefits of your training.

If you’re a serious hard core runner (training up to 2 hours a day), you are effectively depleting your stores during training. The amount of carbs needed on a day to day basis is near the amount required during carbo-loading.FullSizeRender

Runners NEED to EAT!

Now you know that it is important to start off with a full tank!

You wouldn’t drive your car on empty, hey? 😉

Next up, how to reduce dependence on your carbohydrate stores.

Till then,

Keep Running!