When it comes to burning fat, not all exercises and workouts are created equal. Weightlifting, especially compound exercises, and HIIT are two expert-approved ways to burn fat and build muscle. You may have also heard that fasted cardio (nope, it's not a cult-favourite workout class) is another way to burn fat. To find out if this holds true, POPSUGAR spoke to Perri Halperin, MS, RD, a clinical dietitian at Mount Sinai Hospital.
What Is Fasted Cardio?
"Fasted cardio is exercise that increases your heart rate done in a fasted state, or in other words, done when your body is not fed and no longer processing food," Perri told POPSUGAR. "A true fasted state starts at about eight to 12 hours after your last meal," she explained. For example, working out in the morning before eating breakfast qualifies as fasted cardio.
What Are the Benefits of Fasted Cardio?
Working out on an empty stomach may not be ideal for all, but according to Perri, the "benefits of fasted cardio include increased breakdown of fat cells for energy and use of energy from fat cells instead of carbohydrates from a meal or from glycogen (the body's most usable storage form of carbohydrates)." When your body is in a fasted state, your blood insulin levels will drop and your body will begin to use fat as a source of energy instead of carbohydrates, she explained.
Does Fasted Cardio Burn More Fat?
When fasted, your body uses fat as the main source of energy, but does that mean you'll burn more fat as opposed to styles of training such as weightlifting and sprinting? According to Perri, research has shown that you can burn up to 20 percent more body fat doing fasted cardio than fed cardio. If you want to take a break from the weights, you can do fasted cardio and still burn fat. If you're wondering if it's better than other fat-burning workouts, Perri said it isn't necessarily better than strength training or sprinting — "it is just different, and health benefits are improved with all forms of activity and exercise."
How Often Should You Do Fasted Cardio?
According to Perri, every person burns fat and loses weight differently, so there isn't a set amount of fasted cardio sessions you should do in a week. Instead, Perri said to "pay attention to how your body feels when you do fasted cardio. Are you lightheaded? Tired? If so, it may be time to scale back."
"Exercising or doing cardio in a fasted state can cause your blood sugar to drop, which can cause lightheadedness, lethargy, or fainting," she added. If you feel any of these symptoms, consider skipping fasted cardio. Although fasted cardio can burn fat, there's a caveat: not only will your body use energy from fat, but it can also use energy from muscle. Because of this, some people may experience muscle loss, especially the elderly, Perri explained.
If you have diabetes or other metabolic conditions, Perri said to discuss fasted cardio with your physician before implementing it into your workout routine.