Wednesday, 11 March 2009

To burn or not to burn, that is now the question!!

So, there are a few views out there on the topic of my previous article. Do I carbo-load? Do I use sports drinks/gels? Do I rely on my body to burn fat?

Turns out that 1g of body fat can be used by the body to burn 9 calories. Whereas 1g of carbs only burns 4-5 calories. So the body is much more efficient at using its own fat as a source of energy than it is at using carbs for energy. Seems logical I guess... If you’re used to loading on carbs before a big event, then apparently once your body has utilised all the energy from the carbs, that's when you ‘hit the wall’ – the body then won’t be trained to switch to burning fat, so you don't get any new source of energy coming through - hence the use of the sports gels and drinks etc.

If you train the body to use its own fat as a source of energy, then you’ve an endless supply coming through (no comments necessary!). I have pretty much been on a no-carb diet for 4 weeks now so am going to continue along these lines. My diet will include fats that the body can easily break down for energy (nuts are good for this), so hopefully that should be all I need to get through the marathon.

This has been based on the research of (lots of people, but in particular here) a guy that ran across America and holds the world record – something like 11.5 days!! He ran the equivalent of 2 marathons a day, so I think he’s probably worth listening to… Of course he’s not the norm, but my trainer at the gym said for us regular folk if the activity is under 2 or so hours then it doesn’t matter if you carb-load as you won’t run out of energy from the carbs, and if you exercise for over 5 or 6 hours then it will be different, but for those in the middle (about 3 – 6 hours), then it’s better for your body to burn fat than carbs as you’ll run out of carbs when there’s still a loooooooooong way to go… I’ll see how I go over the next 3 or 4 weeks and whether I can see any results as I increase the distances run.

The first test will be the Adidas Half Marathon this Sunday - where we run around the Silverstone Grand Prix track!! Hopefully I'll be more like Hamilton (i.e fast!) than Webber (never sure if I'll finish...). Watch this space...


  1. The body uses different energy systems depending on what is required and what is readily available. Fats are readily available, and this is the energy we run "at rest" or walking. For anything more hectic, the body needs to burn up carbs which takes a lot less time and gets energy to the body more quickly. (Beyond that, activities such as jumping, sprinting or weightlifting, which require a big burst of quick energy, breaking down carbs is too slow and the body taps straight into the ATPs)

    So technically speaking, one practice of "training" your body to rely on fats more is by training to increase your aerobic capacity. In essence, for a person who is not so aerobically fit, at a brisk walk or jog, his body will be telling him "'pant-pant-pant', we need energy to keep going and 'pant-pant' we need it pronto. Burn us some carbs!"

    Whereas someone who is more aerobically fit, at the same brisk walk or jog, his body will not say the same thing until he is required to work a bit harder.

  2. Thanks for that Derek.

    I've found that by relying on fats I'm fine for about 10 - 12 miles. After that I start to get a bit tired, so I think that is where my fitness can take me before it's screaming for carbs.

    Question for you: if I eat carbs, will I burn those first thus use all the carb energy when my fitness doesn't necessarily require it, meaning when it does I've burnt the carb energy rather than the fat energy? Or is it a case that my body won't start tapping into the carb energy until the body requires it?


    In the half-marathon I found taking the sports drinks in the latter half helped, so I think during the marathon I'll take a sports drinks as they are available and water otherwise. I might take 1 or 2 sports carbo-gels as a back up... Even if just as an insurance policy!

    Thanks for your advice Super Coach!