You see this all the time, right? I mean, I used to be one of those people. Wake up at 3, maybe 4 am. Get some black coffee into your system or your pre-workout of choice with some BCAAs to keep you from going catabolic. Hop on the treadmill or stairmaster for the next hour at a low intensity steady state pace. Then, voila, you lost more fat because you did your cardio without eating anything before. Many people still think that this is true, and some light needs to be shed on the truth.
1) You may lose more body fat on an empty stomach, but that’s not all you should look at.
Studies – old and new – find that fasted cardio does not increase lipolysis, but a few recent studies showed that doing cardio on an empty stomach led to 20% greater use of body fat for energy. Here’s the thing though; if you still eat over your caloric maintenance level, it doesn’t matter how much fasted cardio you do, you’ll still gain fat. The major factor to look at and adjust when things aren’t going smoothly is your macronutrient intake. You could do 3 hours of cardio every single day for all I care, but if you’re eating like a pig and going over the amount of calories you’re expending everyday, it won’t mean anything.
2) Pay attention to OVERALL caloric expenditure, not just the amount of calories burned during the cardio session.
With the studies on cardio in a fasted state that I mentioned in number one, they were done to focus solely on the amount of calories burned DURING the session and that’s it. This is a problem once you start talking about HIIT cardio (high intensity interval training). This is because HIIT’s real benefit is the EPOC effect it produces, or the amount of calories you burn once the session is over, for the rest of the day! Study after study proves that HIIT is way more effective than steady state cardio for fat loss, even if the low intensity cardio is done in a fasted state. And that’s because once you’re done with your fasted LISS cardio session, you’re not burning any more calories. With HIIT, you burn calories for another 8-16 hours AFTER your session has been complete. Yes, so when you finish your HIIT session at 11 am, you’re still burning calories and fat at 8 pm while you’re on the couch watching TV, assuming your nutrition program is designed to keep you in a caloric deficit. Even better, eating before your workout or cardio increases your EPOC, compared to a fasted state.
3) It’ll depend on your goals.
Can you lose fat doing fasted cardio? Absolutely, but you can also lose fat by just lifting weights, or running hills, or doing circuits, etc. The big question we’re trying to get at here is “does fasted cardio lead to greater weight loss” and that answer is no. You can’t listen to the guy who swears by fasted cardio just because “it works for him”. That’s a personal opinion and will never be a substitute for scientific reality. If your goal is to become skinny, I’d do hours of steady state fasted cardio, but if you’re reading this article, you likely do not want to be skinny. You most likely want to lose body fat, get ripped, and retain – or even gain – muscle tissue. That means you want to focus on protein retention and limit protein breakdown, but by exercising while you’re in a fasted state, you may double protein breakdown, meaning your muscles are trying their best not to be eaten alive. Better to eat and have an amazing training session, than to be fasted and putter along like a turtle.
At the end of the day, you can do cardio fasted, after you eat, right before you go to bed, whatever works best with your schedule, because cardio is nothing more than a tool utilized to expend more energy (calories). As I stated before, make sure your macronutrient intake is sufficient and your total caloric intake is optimal to support muscle retention and body fat loss.
Train hard and train smart.