16 Jun The Difference Between Fasted Cardio and High Intensity Interval Training (HIIT) – Expert Thomas DeLauer
If you’ve been immersed in the fitness world for long enough, you will eventually become familiar with fasted cardio and HIIT cardio. These two different types of cardio have essentially become rivals within the fitness community, and many people swear by one, while claiming the other is detrimental. There is a saying that goes something like “There’s three sides to every story. Yours, mine and the truth”. So in order to figure out the truth behind which of these forms of cardio comes out ahead, we first have to understand what they are and how they affect your body.
Fasted cardio is cardio that is done while being in a fasted state, hence its name. But more than that, it involves how your body processes and absorbs the foods you eat. When you eat, food gets broken down into energy that your body uses. As your body is absorbing what you’ve eaten, your insulin levels increase and you are in what’s known as a fed state. However, when your body has finished absorbing nutrients, your insulin levels decrease to their baseline level, and your body is now in a fasted state. Insulin plays an enormous part in weight gain and loss, as it impairs the breakdown of fatty acids.
Think of food like gasoline in a car. Your car has a gauge to tell you how much fuel you have left. When your car is full, why would you want to put more gasoline in the tank for it to burn through? This is much like your body’s relationship with food. Your body wants to take the easy road and utilize the energy stores (gasoline) that are the easiest accessible, and food is much easier for your body to break down and utilize as an energy source, instead of converting fat stores to energy. So why would it want to burn fat for energy when energy is much more readily available via the food we just ate? As your body processes and absorbs the food and you are entering a fasted state, your insulin levels decline, which tells the body to start utilizing fat for fuel instead of food energy. So, in short, when you are in a fed state and your insulin levels are high, your body will be burning food for energy instead of fat.
This is where fasted cardio comes in handy. Jumping on the treadmill first thing in the morning while your body is still in a fasted state will pull energy from fat stores instead of utilizing food for energy. These fat stores provide a sustainable form of energy that can fuel your cardio for up to 30-45 minutes before beginning the breakdown of muscle tissue. Fasted cardio is extremely effective for burning fat so long as you don’t go overboard and keep intensity levels low to moderate.
HIIT cardio is otherwise known as High Intensity Interval Training. This typically involves alternating between an intense 30-60 second burst of an exercise, then slowing it down for milder 30-60 seconds of the exercise and repeating. However, more recent evidence is showing that HIIT cardio is best performed when the rest periods are longer and allow for appropriate recovery of the muscles being used. When you perform HIIT cardio, your body acts in a similar manner to how it would if you were performing a bout of strength training. You achieve all the benefits of regular cardio, but with some added metabolic benefit in the sense that your body continues to burn calories for an additional 24 hours after the workout is completed. This is extremely effective if you’re trying to preserve lean muscle.
It is imperative, though, that when you do HIIT that you allow yourself adequate recovery between your intervals. For example, if you are running sprints for 30 seconds, you will likely need more than 30 seconds of recovery in order to perform at your maximum potential for your next interval. HIIT is most effective when you can focus close to 90% intensity to your interval and allow for full recovery. That being said, you generally only need about 6-8 bouts of intervals before you have sufficiently tapped into the metabolic furnace that you have inside!
Which Is the Winner?
So what kind of cardio should you do, and which is going to be more effective at burning fat and helping you develop a lean, toned body? The answer truly is both! Just like with anything in life, too much of a good thing is never healthy. Too much fasted cardio will likely begin to reduce muscle mass and too much in the way of intervals can lead to overtraining and the eventual ineffectiveness of HIIT. If you condition your body to become extremely efficient at performing intervals, your body will begin to adapt to the intensity and will no longer use the usual energy stores to fuel that workout. The simplest way to put this is that your HIIT cardio becomes no different from your regular steady-state cardio at this point. It’s almost like your body is telling you that you’re getting TOO good at cardio.
So switch it up. Use some fasted cardio for a week or two, and then embrace the metabolic benefits of HIIT for a couple of weeks. There is nothing that says that we have to become a slave to one specific form of cardio. There are no sides here, we are all simply trying to get leaner, and live happier, healthier lives!