6. Surely we need carbs to fuel us during exercise?
No.
When we’re eating a diet that’s high in carbohydrate (the diet that’s currently still recommended by the NHS), this is what your body will burn for fuel. Carbohydrate is converted to glucose in your body, and there are three ways that the body uses this fuel:
- as an immediate source of energy (think of the boost you get from sugar/chocolate as an example of this)
- stored for later use as glycogen, in your muscles and liver
- stored for longer term needs, as fat
If all we’re doing is eating lots of carbohydrate, we only ever access the first two stores – the danger being that the third store, fat, increases more and more.
When you take exercise, you’re accessing stores 1 & 2. But this is limited in terms of what it can supply to your body by way of energy – this is why runners and cyclists talk about ‘hitting the wall’ or ‘bonking’ – at a certain point, you’ve exhausted all the readily available energy in stores 1 & 2. This is why all the high-sugar gels and energy bars and drinks have been created for athletes – they need a quick ‘fix’ of glucose for extra energy.
We all have fat that the body can access for energy – even endurance athletes who have a very low body fat, but it’s difficult to access the third store, as your body isn’t used to burning fat for energy.
This is where low carbing comes in, and it’s why the first two weeks of Bootcamp are so strict. The aim is to switch your body from burning carbs (glucose) for fuel, to burning fat. This process of fat-adaptation isn’t immediate, but a strict couple of weeks will see you well on the way to achieving this.
Once you are fat-adapted, you have plenty of fuel for exercise.
In the short term, while your body is making the transition from burning carbs to burning fat, you may find exercise more difficult than usual – but this is only temporary.
A really good book to read here is “The Art and Science of Low Carbohydrate Performance” by Drs Phinny and Volek. They’ve done tons of research into this.