What Type of Fasted Cardio Is Best?
If you’re familiar with my work, you know that when it comes to cardio, I’m a big fan of high-intensity interval training.
Studies such as those conducted by Laval University, East Tennessee State University, Baylor College of Medicine, and the University of New South Wales have conclusively proven that shorter sessions of high-intensity cardio result in greater fat loss over time than longer, low-intensity sessions.
In fact, a study conducted by The University of Western Ontario showed that doing just 4 to 6 30-second sprints burns more fat over time than 60 minutes of incline treadmill walking (one of the staples of “bodybuilding cardio”).
Furthermore, keeping your cardio sessions shorter helps you preserve muscle and strength.
This is especially relevant to fasted cardio as it accelerates muscle degradation, and the longer you train in a fasted state, the more muscle you lose (we’ll talk more about how to combat this in a minute).
All that said, some people say HIIT performed in a fasted state is silly because fat oxidation rates are much lower during HIIT exercise.
Well, while it’s true that fat oxidation rates decline as cardio intensity increases (as carbohydrate then becomes the fuel of choice), there’s more to consider.
- Research has shown that as you continue to perform regular high-intensity interval cardio sessions, your muscles “learn” to use less carbohydrate during workouts (thus increasing fat oxidation rates during the workouts), and your muscle cells also get better and better at oxidizing fats.
This latter point is particularly relevant to fasted cardio as, over time, high-intensity interval training increases the total amount of fatty acids your body is able to metabolize during workouts.
- Research has shown that the post-exercise “afterburn” effect (EPOC) is greater with high-intensity interval training than with low-intensity steady-state cardio (about double, actually—13% vs. 7%).
The actual amount of additional calories burned due to HIIT’s greater “afterburn” effect will probably never be more than 50 to 80, but hey, that adds up over time.
- Research has shown that high-intensity interval cardio is particularly good for getting rid of stubborn belly fat, including the dangerous accumulations of visceral fat.
Given all the above, I think it’s just a no-brainer to choose high-intensity interval cardio over low-intensity steady state.
Some people say doing so puts too much strain on your body and will cause overtraining, but I’ve yet to run into that problem with my own body or the thousands of people I’ve worked with.
(Seriously—I’ve never had one person write me complaining about feeling overtrained soon after incorporating fasted HIIT into their workout routines).
That’s probably because I recommend a very moderate amount of high-intensity interval cardio when dieting for fat loss—no more than four sessions per week, and no more than 25 to 30 minutes per session.
What About Fasted Weightlifting?
Weightlifting causes a dramatic spike in plasma catecholamine levels and as catecholamines are better able to mobilize fat when you’re in a fasted state, fasted weightlifting is also worthwhile.
I do all my exercise—both weightlifting and cardio—fasted when I’m dieting for weight loss and as I said earlier, the stubborn fat disappears noticeably faster than when I do this than when I do all my training in a fed state.
A caveat, though: don’t be surprised if you’re noticeably weaker during your first couple of weeks of switching from fed weightlifting to fasted.
You will lose some reps on your big lifts, if not across the board. This isn’t because you’re losing muscle, it’s simply because eating a significant amount of carbohydrate before you work out dramatically improves your performance in the gym. Take the carbs away and you lose the “boost.” Add them back and it returns.
That said, as I noted earlier, your body slowly adapts to training in the fasted state, learning to preserve carbohydrate during training, and thus maintain performance. Nevertheless, I’ve found that my lifts while fasted are just never as good as my lifts while fed.