Fat Burning Efficiency by Marc Laithwaite

Image ©getphysical.co.uk

Image ©getphysical.co.uk

Last week we talked about the possible benefits of high fat coffee (Bullet Proof Coffee) prior to an endurance workout. Greater levels of circulating fats in the blood stream, may promote the use of fat as a fuel source and thereby saving precious carbohydrate stores. It created quite a stir… as we expected!

As a recap, when you run long distances, you use a combination of both fat and carbohydrate to provide energy. Your objective is simply to get the most energy as possible from fat and less from carbohydrate, as your carbohydrate stores are relatively limited and can run out quickly.

For example: If when running at an endurance pace (say long ultra) you currently use 600kcal per hour with 30% coming from fat and 70% coming from carbohydrate, that’s 420kcal of carbohydrate per hour. If you reverse this figure so only 30% of your energy comes from carbohydrate, then you will only use 180kcal of carbohydrate per hour. That is a saving of 240kcal of carbohydrate per hour (60g per hour), which is actually the recommended intake during most endurance events!

So if the recommended guidelines are to ingest 60g of carbohydrate per hour during endurance events (that’s approximately 1-2 bars or 2-3 gels) and you switch your fat usage from 30% to 70%, then technically you don’t need to take any fuel right??

Not quite… even if you optimise your diet and training to enhance your fat usage, you’re always going to be using carbohydrate to some extent, so you still need to take it on board. There are a couple of key things you need to take into account:

  1. If you’re rested, tapered and fuelled, then you should be starting on a full tank of carbohydrate, so eat a good source of carbohydrate in the days prior to racing.
  2. We are obsessed with carbohydrate portions, thinking that more is better and a bigger portion equates to more glycogen (stored carbohydrate). Your glycogen stores are relatively small, so you don’t need to eat a lot. If anything, eat a little less in the final days to stop yourself feeling bloated and heavy. This is difficult to do, as we generally believe that ‘carbo loading’ is required so eat excessively in the final few days. The same rule applies for breakfast, a huge meal is of no benefit as your stores are probably already full.
  3. If your fat usage is enhanced, you don’t need to eat as much during the race or training. In Ironman many people ‘panic eat’ on the bike with a fear that we won’t have enough fuel on board. There is a real trend for people to be obsessed with how much they can eat during the cycle section. Athletes often have a set plan of several bars and gels, plus energy drinks at regular intervals. Stomach problems are very common due to high amount of carbohydrate, which gather in the stomach, leading to bloating.
  4. The most common reason given for people failing to hit their target times in endurance events is ‘I got my nutrition wrong in the race’. The truth of the matter is that you got your training wrong.

Last week, we suggested that Bullet Proof Coffee or training in a fasted state works best when training for 1-3 hours, depending upon your sports and ability. But what if you’re going further? What if you’re running for 3-5 hours or cycling 5 hours or more? For many athletes, riding for 5 hours in a fasted state would create a very high level of fatigue, which may take several days to recover from and impact upon your normal weekly training. If you are riding or running longer distances, breakfast and food throughout the session is needed and you should follow these guidelines:

  1. Eat food which will maximise fat usage to save carbohydrate.
  2. Maintain a constant blood sugar level and avoid spikes and dips.
  3. Based on point 2, eat foods which provide a slow ‘drip feed’ of energy rather than those which give you an instant hit.

Here are examples:

Breakfast is 1 mug full of muesli with no sugar. To increase fat content, buy mixed seeds/nuts breakfast cereal topper and add quarter of a mug. To further increase fat content sprinkle on desiccated coconut. Add dried or chopped fruit (anything low GI) and eat with full fat milk or natural yogurt. Don’t add any sugar, honey or syrup. It should be a small to medium bowl, don’t overeat and try to stock up with extra toast and jam for carbohydrates.

During exercise eat nothing for the first hour then take something every 30 minutes. You need to avoid things, which give you an instant hit, so avoid all high sugar products and don’t use energy gels. Energy bars take longer to digest so half a bar every 30 minutes would be suitable. Opt to have half every 30, not a full bar every hour, as this is easier for your stomach and intestines to deal with. You can choose something different to sports bars, such as flapjack, dried fruit or bananas. If you make your own flapjack, butter, fruit, coconut and oats are good, avoid sugar and syrups. The key is small quantities frequently (every 30 minutes from 60 onwards), coupled with water, squash or electrolyte solution, but no energy in drink.

The great gel quandary

Gels were invented for a specific purpose. When you felt low on energy and you were about to ‘bonk’ or ‘hit the wall’, you took a gel and it gave you instant energy. They gave you a rapid sugar spike at times when a rapid sugar spike was required. Then at some point the rules changed, gels were no longer a rapid source of energy for low periods, they are now to be taken every 20 minutes to provide a constant flow of energy. Simultaneously we are advised that we need a constant drip feed of carbohydrate and to avoid sugar spikes. Maintaining a steady blood sugar level is key to efficient metabolism. I’m not sure if I’m the only one confused, but I’m not sure how taking a product designed to spike your sugar levels every 20 minutes can be described as ‘drip feeding carbohydrate’ and maintaining a steady supply. In fact, gels sold based on their ‘fast acting’ properties, would surely be the worst things to take? That of course depends upon how you’re using it, if you’re taking it every 20 minutes to top up energy through a long race, the statement is correct. If you’ve bonked and you need an instant hit, then a gel is perfect, as that’s what they were designed for. It’s interesting how the purpose of a product can change, but I guess if you only took gels when you ‘bonked’ compared to buying 18 of them for a 6 hours ride, the gel economy would take a hit. Just saying.

What next?

As a start point, go out and ride or run and try the strategy. Don’t panic eat or over-eat either before or during. Choose low sugar foods in small quantities at frequent intervals and don’t be afraid of ‘bonking’ during this process. It may take your body a while to become accustomed to utilising fat so give it some time.

Pacing is key

Pacing is the missing jigsaw piece for this strategy. Riding or running at the correct intensity is critical during training sessions if you wish to maintain glycogen stores for the full duration of the workout. We’ll discuss pacing in next week’s blog and how intensity impacts upon fuel usage during endurance training and racing.

– Marc Laithwaite

About Marc:

Sports Science lecturer for 10 years at St Helens HE College.

2004 established The Endurance Coach LTD sports science and coaching business. Worked with British Cycling as physiology support 2008-2008. Previous Triathlon England Regional Academy Head Coach, North West.

In 2006 established Epic Events Management LTD. Now one of the largest event companies in the NW, organising a range of triathlon, swimming and cycling events. EPIC EVENTS also encompasses Montane Trail 26 and Petzl Night Runner events.

In 2010 established Montane Lakeland 50 & 100 LTD. This has now become the UKs leading ultra distance trail running event.

In 2010 established The Endurance Store triathlon, trail running and open water swimming store. Based in Appley Bridge, Wigan, we are the North West’s community store, organising and supporting local athletes and local events.

Check out the endurance store HERE

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2 thoughts on “Fat Burning Efficiency by Marc Laithwaite

  1. Thanks for an interesting article. After being diagnosed with type one diabetes in 2013 and taking up ultra running, I now consider myself quite an authority on blood sugar control, given that I have to test my blood sugar multiple times each run! After my diagnosis I started doing aerobic training (HR of 143 for most of my runs) for the first time in my life – this has made a big difference to fat burning. I’ve noticed that over time I need to consume less carbs during running to maintain constant blood sugar. I’ve shared some of my data here: http://wp.me/p3OESN-7n. I also agree about carbo loading – I eat a higher percentage of fat now and always exercise in a fasted state so that I can run safely without hypos. I always have enough energy.

    Before the CCC last year I stuffed my face with pasta the day before and had a massive bowl of porridge and fruit before the race. I felt bloated and my blood sugar stayed high with no need for me to eat for 55km! Next time I will eat less.

    I drip feed jelly babies, cereal bars and pita bread when I’m running a long way. Gels cause too much of a sugar spike as you say.

  2. Great article!
    It’s not just a matter of fueling either – many (arguably most) people will also improve their health biomarkers when they remove or reduce sugars and processed carbs from their normal diet. Fueling primarily from fat metabolism should be the normal modus operandi in healthy people. Dr Maffetone’s philosopy which you discussed on the podcast recently has always been adamant the athletes who can handle the most training gain the most benefit from it are those who are the healthiest.

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