Chances are you’ve heard of or even tried fasted cardio. It’s been raved about by fitness enthusiasts and promoted as an excellent way to burn fat for quite a while now.
Which is correct.
But it isn’t the ONLY way. We hope you read on after this but the only way to lose or gain weight is to consume more calories than you burn or burn more calories than you consume.
Calories in > Calories out = Weight gain
Calories in < Calories out = Weight loss
Calories in = Calories out = Weight maintenance
But why the craze around fasted cardio and does it actually work?
What is it?
Fasted cardio means performing cardiovascular exercise (continued rhythmic exercise that increases the heart rate) on pretty much an empty stomach.
Often this is done first thing in the morning, when the body is in a fasted state, without having consumed food.
How does it work?
The hypothesis behind this method is that by not consuming any “energy” (food) the body must utilise its own stores of energy (body fat) to perform the activity. This in turn increases fat oxidisation and results in greater fat loss.
In theory, due to fasting, low glycogen and insulin levels cause the body to shift energy utilisation away from carbohydrates, thereby allowing greater mobilisation of stored fat for fuel.
Does it actually work?
Despite the theoretics behind this approach, evidence from several studies show whether in a fasted or fed state, weight loss is attributable to hypocaloric diets rather than timing of exercise and exercising in a fasted or fed state. That doesn’t mean you should stop doing it.
Studies tend to show exercising in a fed state does have an impact on and reduces fat oxidisation, due to "free flowing" glycogen being used up rather than stored glycogen and a reduction in fatty acid transport and oxidisation. Regimented fasted training can also promote improvements to the body's tolerance to glucose and sensitivity to insulin. However the difference in results in minimal.
To summarise. Whether you prefer to fuel before cardio or perform cardio on an empty stomach, as long as you are following a low calorie diet (one that is also suitable and sustainable to you) or are burning more calories than you put into the body, weight loss and effectively fat loss will be a result.
Remember 1lb of body fat estimates around 3500 calories. Therefore to lose 1lb of body fat a week (a safe loss according to the NHS) you will need to be in a calorie deficit of at least 500 calories per day, for 7 days!