In broad terms, the theory behind fasted training is to ‘force’ your muscles to burn more fat for fuel instead of carbohydrate.
It ‘works’ in theory up to a point, but there are many variables involved. “People have found it useful for weight loss but research has shown that, that’s actually purely because of eating less ie a calorie deficit. Which is what you need when losing weight,” explains ASICS FrontRunner and registered dietician, Mariella Sawyer.
Put simply: To lose weight, you need to be in a calorie deficit – that is, you must consume fewer calories than your body needs over a period of time (several days) and not one single run.
According to Mariella, you’re putting your body under additional (and perhaps unnecessary) stress by training in a fasted state. “You’re not fuelling it for your sessions meaning performance and recovery is negatively influenced and your immune system becomes more strained too, increasing your risk of getting sick,” she says, adding that you might also not be able to push your sessions because your glycogen stores are depleted. “Not much point training at all because you can’t get a lot out of your session anyway,” she says.
Mariella also doesn’t necessarily buy into the “it increases fat oxidation” theory, at least not if you don’t adjust your diet accordingly. “If you train fasted and then eat carbs etc, that is what your body will burn,” she says.
The jury is out and it is (as with most nutrition theories) a case of ‘what works for you’ …
If you do want to try training fasted (first thing in the morning), start with low- or moderate-intensity exercise (as you’ll be burning relatively more fat and less carbohydrate).
And, tell us what your thoughts are on the subject.
