VRP Nutrition Blog 2

Nutrition During Exercise…

By the time you read this, you will have completed week 1 of VRP, so congratulate yourself! Getting the first week ticked off is often the hardest, but it is also what we need to bed down a good habit. Our group page has really come into it’s own by keeping us engaged, accountable, motivated and open to new food choices!

So, in last weeks blog we looked at fuelling our bodies before running by looking into carbohydrate and it’s role. We are now going to move this on and delve into the exciting subject of energy demands during exercise and mainly looking at the role of carbohydrates and also fats.

It is important to understand a little about which fuels are most important for exercise and us athletes (do you like how I referred us to athletes again?😜)

We mentioned Carbs, but fats and proteins can also provide our bodies with energy. Proteins are not a major source in terms of fuelling but can have a part to play in the latter stages of a long, endurance event when all glycogen (carbs) and fat have been utilised so we will come back to protein in my next blog when we talk about recovery foods as they score highly here. 

Fat on the other hand can be a good source of energy, even more efficient than carbohydrate (glycogen) in fact. Fats release energy very slowly which makes them a very energy-efficient form of fuel. Each gram of fat supplies the body with about 9 calories, this is more than twice that supplied by proteins or carbohydrates. Due to fats being such an efficient form of energy, the body stores any excess energy as fat. So, why do we need glycogen and why not use solely fats I hear you ask? Well, the factors that help our bodies decide whether to use carbohydrate or fat depend on the following:

  • The intensity of the exercise
  • The duration
  • Your fitness level
  • Your pre-exercise diet


The higher the intensity (anaerobic exercise), the greater the reliance is on glycogen/carbs, for example any HIIT type exercise and maximal bursts like beach sprints will utilise glycogen. The reason for this is that when our body lacks oxygen (we are struggling to breath) due to us working at a maximal intensity, our body can rapidly break down glycogen to provide us with energy without the need of oxygen unlike fat can. Fat very much struggles to break itself down quick enough to provide us with the energy we need at this intensity.

When we exercise at a moderate intensity, we are able to take in more oxygen (aerobic exercise) and at this point the body switches to approximately using half our fuel from glycogen and half from fat. This could be in your tempo runs for example. 

As we take the intensity down even more like we should in our ‘easy’ run days and also to a degree our Sunday long runs where the pace is slower, our body uses mainly fat as our fuel source. I think this really highlights how to fuel our bodies on particular run days don’t you think? Food for thought… Ha, excuse the pun. 


Duration plays a big part in how long we can utilise glycogen. Glycogen cannot provide energy endlessly as it is stored in relatively small amounts in our muscles and liver. As you run for longer, the glycogen levels progressively lower which is where fat comes to the rescue and provides energy. On average you have enough muscle glycogen to fuel you for 90-180 minutes of endurance exercise remembering the higher the intensity the faster the glycogen stores will be depleted. So when doing a Saturday Run session with YNM which is a mix of interval work using both aerobic & anaerobic activity stores will more likely deplete after 45-90 mins. It is worth noting this when thinking about what you might eat before a Saturday or similar session as glycogen stores that we need for the fast intervals could be depleted before the end of the session which will not only make the last 15 mins VERY hard but of course this will affect our performance and pace as our bodies switch to more of a fat source. 

Fitness Levels:

As we gain more aerobic fitness our muscles make adaptions which in turn improve our performance but also our body gets better at using fat as a fuel and breaking it down. As your muscles gain more muscular endurance benefits, the better they can break down fatty acids in each muscle cell which allows you to spare glycogen at every intensity which is important as glycogen is in shorter supply than fat. By using more fat you will be able to exercise for longer before glycogen is depleted and fatigue sets in! Win win situation in my book 😉

Pre- Exercise Diet

So you can see how this is an important area. A low-carb diet will = low glycogen stores which will effect performance and your ability to sustain exercise for longer than 1 hour. It will also affect your ability to perform at shorter, maximal output. 

When glycogen is low your body will depend on fat and protein, which is not ideal or efficient. 

The best bits… Food. 

We have spoken about good sources of Carbohydrates and now I’m going to talk about Fats. 

Now I think it’s fair to say that Fat is essential in our diet especially as athletes 😉 It contributes substantially to our cell membranes, brain tissue, nerve sheaths and bone marrow and also provides essential fatty acids. It provides fat-soluble vitamins A, D and E and is a VERY important source of energy to us runners! 

We often hear everyone bang on about Omega 3 and there is a very good reason for this as it helps the delivery of oxygen to our muscles, speeds recovery by reducing inflammation and joint stiffness.  

In simple terms, fat comes in two sources:

Saturated fatty acids which we find in foods like:

  • Butter, ghee, suet, lard, coconut oil and palm oil
  • Cakes
  • Biscuits
  • Fatty cuts of meat
  • Cured meats like salami, chorizo and pancetta
  • Cheese
  • Pastries, such as pies, quiches, sausage rolls and croissants
  • Ice cream
  • Milkshakes
  • Chocolate and chocolate spreads

Un-Saturated Fats:

  • Avocados and avocado oil.
  • Olives and olive oil.
  • Peanut butter and peanut oil.
  • Vegetable oils, such as sunflower, corn, or canola.
  • Fatty fish, such as salmon and mackerel.
  • Nuts and seeds, such as almonds, peanuts, cashews, and sesame seeds.

The proportion of our fat intake that makes up our diet should be around 25-35% calorie intake for athletes. Try to limit the percentage of fat intake that comes from saturated and concentrate on the yumminess of the un saturated fats by including more of them in your diet. 

In my world, nuts are an absolute must, They are my go to snack and seeds are just fantastic to add to salads, pastas, cereal, porridge, smoothies and all sorts to add that extra crunch to a mouthful of goodness. Don’t get me started on the all important avocado and the olive oil that we seem to go through!

Of course it’s important to find a combination of foods from the food groups that I have mentioned that you actually like. There is no point using my friend the avocado in a sandwich if you hate them, find something that you do like so that it has longevity in your diet and enables you to be the best that you can be when it come to lacing up those trainers 😜

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