There has been a lot of debate surrounding the topic of Fasted Cardio, and whether or not it is a beneficial tool for fat loss. Like all things health and fitness, it is important to think critically about all fads and theories, and to determine what works best for your body.
For those of you who don’t know, fasted cardio is when you do cardio in a fasted state (typically first thing in the morning). Why do fasted cardio? It is said that doing cardio on an empty stomach is an effective tool for burning fat. Let’s look at the pros and cons to fasted cardio.
Benefit #1 When doing morning fasted cardio your body is using free fatty acids as energy. As you sleep, and fast overnight your body conserves its carb stores and utilizes fat for energy. Your body also breaks down amino acids into glucose wile sleeping, so when you do fasted cardio your body mobilizes more fat for fuel.
Benefit #2 When doing steady state fasted cardio, the glycogen in your muscles are spared for energy since there are free fatty acids floating around your body.
Benefit #3 You may be able to afford eating more carbohydrates if you perform fasted cardio. Since your insulin sensitivity is high during fasted cardio, when you eat carbs after fasted cardio your body will want to replenish the glycogen stores in your muscle and tree fore, the carbohydrates will go to your muscle rather than being stored as fat.
As mentioned above, your body breaks down amino acids into glucose while you are sleeping. While doing fasted cardio your body may utilize some amino acids for fuel, which is not ideal if your goal is muscle building. This will become more problematic if you participate in HIIT or interval training in a fasted state. With fasted cardio, your cortisol levels are very high (a muscle wasting hormone), and thus cortisol will lead to use amino acids as energy. Since you have not eaten any protein, your body will pull the amino acids from your muscles.
Some other research argues that fat loss can be maximized after consuming some protein and carbs since you will have more energy to push yourself during cardio or HIIT, and thus, burn more calories.
Everyone is different and has various goals. It is important to choose an exercise program that aligns with your goals, schedule, time and lifestyle. If your goal is to build muscle, then perhaps fasted cardio is not for you. If you have a busy schedule and only have an hour to train, then you should maximize your time at the gym and do weight training. That being said, if you are eating clean and are weight training and still want to lose fat, fasted cardio may be the right solution for you.