What is it? Fasted cardio is exactly what it sounds like: doing cardiovascular exercise (running, swimming, biking, etc) on an empty stomach after not having eaten for a while. Fasted cardio is typically done before breakfast.
Why do it? Fasted cardio is effective because your body uses fat for energy. Overnight, you are not eating but your body is still functioning, so your body uses glycogen (energy stored in your muscles) for energy until the next meal, breakfast. So when you wake up, your glycogen will be depleted and your body will use stored fat for energy.
This may not work for everyone, since we are all different, but if you can do it, it’s an amazing tool for fat loss. Just 20-30 minutes in the morning before having breakfast can have a huge impact! You can choose to do it every day, every other day, or however often fits your schedule. I advise starting with 15 minutes and working your way up if you are new to this. **You need to make sure your body can handle this!** If you feel weak or faint I do not recommend exceeding one hour, although even that is very ambitious.
My main point of focus right now is my abs. I want to get them really tight and flat and I’ve implemented fasted cardio 3-4 times a week to do it. I only did it four mornings before I started to see a difference so I can definitely vouch for it!