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Fasted cardio: fitness fad or fat-loss secret?


Do you jump straight out of bed into your morning run or a heart-starting HIIT session? You may not have realised it, but this makes you a member of the fasted cardio club.

There’s a lot of buzz around fasted cardio as a weight-loss accelerator, and at first glance, it seems to make sense: If you exercise on an empty stomach, your body will be forced to draw on fat stores for energy – so surely that means you’ll burn more fat overall and lose weight faster, right?

Well, not quite. While we’d love to tell you that losing weight is as simple as this one simple trick, our bodies are a tad more complicated than that. Let’s investigate...

Does fasted cardio really work?

When we say ‘burning fat’, we’re actually talking about the process of fat oxidation – the breaking down of fatty acids to be used by your body as fuel. And yes, it has been shown that fasted cardio will increase fat oxidation. But – and it’s a big BUT! – there is no evidence that it makes any difference to your overall body fat.

In a study of cyclists split into fed and fasted groups, researchers found that while subjects did start oxidising fat after 80 minutes of exercise, there was no evidence that training on an empty stomach was an efficient way to reduce total body fat. Other studies have likewise concluded that training in a fasted state does not result in a reduction of body fat – at least not enough to make any difference to your waistline.

In a nutshell: While endurance cardio sessions force your body to draw on fat as a fuel source, you won’t burn through enough to result in faster or more significant fat loss.

Pink, green, yellow and purple smoothies from the Emily Skye FIT meal plan.

You don’t need to fast to see results. Why not fuel your morning workout with one of the most popular FIT smoothies?

Food is not the enemy

The FIT food philosophy is all about fuelling your body well to train at your maximum intensity. As our resident Advanced Sports Dietitian Lisa Middleton says: “You might be able to do a lower-intensity workout a little bit hungry, but don’t leave your body without any fuel when you’re trying to do your best.”

Researchers from the cycling study agree. They concluded that it was quite possible that fasted training “would produce inferior results” to training with something in your stomach.

If you struggle to eat a solid meal first thing before you train, a smoothie or a small snack – like the Choc Peanut Butter Protein Balls – might be your best bet for giving your body the nutrients it needs to smash your early-bird workout.

So should I ever be training in a fasted state?

If you’re an endurance athlete (think triathlons or marathons) in need of a backup fuel source when you ‘hit the wall’ in the heat of competition, training in a fasted state may have some small benefits.

But if your goal is to lose weight, sculpt a lean and toned body or build muscle and strength, forget the fasted cardio and eat up!

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