Running on empty usually makes working out harder, but studies have shown that low-intensity aerobic exercise in a fasted state – before breakfast, for example – can foster long-term improvements in performance and weight loss.
Why you would:
Normally, exercise uses a combination of glycogen (carbohydrates) and fat as fuel, but – according to a recent study published in Sports Medicine – exercising in a fasted or glycogen-depleted state creates adaptations in the body’s fat oxidising abilities, meaning that the body will turn to fat for fuel and will potentially retain this trained ability when it comes to endurance performance. So you’ll sustain energy for longer without turning to sports supplements.
Will it help you lose weight?
Not if you’re adequately refuelling afterwards. “If you want to lose fat there are other more appropriate mindsets for training and eating,” says exercise physiologist Jodie Hopkins. “If you are fuelled before your early-morning training, you get more bang for your buck: better performance, more enjoyment and better fuel source activation.”
The same study recommends that fasted cardio be performed at a low absolute intensity for extended periods of time. To mediate the effects of glycogen depletion (aka, feeling like you’ve hit a wall before you even start), the researchers recommended a carbohydrate-free caffeinated drink or a mouth rinse.
Fasted training isn’t a training method you’d use every day, especially if you want to keep getting the most out of your training. “If you are low on glycogen the brain knows it, and it will just slow you down or stop you earlier,” says Hopkins. If you’re using fasted training in an attempt to better endurance performance, it’s best to combine it with other higher-quality sessions.
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