Allowing the body to burn fat more efficiently, advocates of fasted cardio – working out on an empty stomach – claim it results in a more effective workout. However, recent studies suggest this may no longer be true, indicating that fasted cardio is a short-term solution to aid weight loss but, in the long run, can lead to muscle wastage, increased levels of the stress hormone, cortisol, and compromise a lean physique. SL caught up with Personal Trainer Monty Simmons for the lowdown...
Firstly, how does fasted cardio work? Fasted cardio, or working out on an empty stomach, is usually done first thing in the morning. Glycogen is the stored carbohydrate the body uses as its preferred fuel source during exercise – the fasted cardio crowd claim that because glycogen is somewhat depleted in the morning after a night’s fast, your body will look to burn fat instead of carbohydrates during exercise. A recent UK study found those who partake in fasted cardio first thing in the morning can burn up to 20% more fat than if they had had a meal beforehand.
Okay, so what are the other benefits? Advocates of fasted cardio claim it gives them more energy, keeps them focused and means they avoid tummy troubles and stitches, particularly if running or high impact exercises are your thing. Studies have also shown fasted cardio may help to optimise our hormones – including insulin resistance and growth hormone (GH) – for enhanced fat loss and improved blood flow to the muscles.
Fasted cardio is a great way to kick-start the day, you’ll build an appetite for a balanced breakfast and get a healthy release of dopamine. However, it’s important not to go too long without replenishing the nutrients in your body – aim to do fasted cardio within 30 minutes of waking up.
And what are the downsides? It can lead to muscle wastage – since you have no new source of energy in your system when running on empty, the body turns to muscle to break it down for glucose (i.e. quick energy). In the long-term, working out on an empty tummy can lead to excessive levels of cortisol (the stress hormone) in the body, which can contribute to weight gain, particularly around the middle section.
If you do a fasted workout, be very strict about eating adequately as soon as you can post-session – aim for a meal made up of around 40% carbs, 30% protein and plenty of vitamins, minerals, fibre and phytonutrients.
Does fasted cardio burn more calories? This is where things get complicated – studies show fasted cardio burns more calories as it requires you to breathe harder, utilise more oxygen and raise the heart rate. However, focusing on calorie burn alone is problematic as the real benefits of exercise come after working out – with the so-called ‘after-burn’, as you continue to torch fat and calories up to 24 hours after a workout – and studies into fasted cardio focus solely on how many calories are burned during exercise alone.
Ideally, the body should be fuelled for HIIT sessions to have maximum effect – have a smoothie or some eggs around two hours before to give you the nutrition you need to fuel an intense workout. When performed correctly, all exercise will burn fat in conjunction with a healthy diet.
What’s the general rule on eating before and after a workout? Little and often is key. Eat regularly, around every two to three hours, even if it’s something as small as 40g of mixed nuts. In terms of eating after a workout, focus on more carbs for energy and replenishing as well as protein for repairing.
The bottom line? Ultimately, what you do, or don’t, eat before exercise is dependent on how you feel. Listen to your body and fuel your workout with a light snack an hour beforehand if you feel you need the energy. In short, if your goal is weight loss, fasted cardio may benefit you temporarily. But if your goal is strengthening your muscles and becoming more toned, it may hinder your progress.
For more information, visit MontySimmons.co.uk