What Is Fasted Cardio?
The biggest misconception about fasted cardio is that it just means doing cardio on an empty stomach.
What it actually means, though, is doing cardio when your insulin levels are at their lowest (baseline) levels.
Insulin is a hormone which is released when you eat food.
When you eat a meal consisting of protein, carbs, and fats, your body breaks down those nutrients into amino acids, glucose, and fatty acids, which are released into the blood stream.
Insulin's job is to escort those nutrients into cells where it they can be utilized or stored.
But Insulin does more than just shuttle these nutrients into cells. It also tells the body to stop burning fat and start storing it.
When your Insulin levels are high, your burning less fat.
When your Insulin levels are low, your burning more fat.
And so, as the story goes, fasted cardio increases the amount of fat you burn because, when you're in a fasted state and your Insulin levels are low, your body will naturally burn more fat.
Fasted Cardio Isn't That Effective Of A Fat-Loss Strategy
People do fasted cardio because they think it will help them lose fat faster. I mean, it sounds good in theory.
Since your insulin levels are low, you burn more fat. Right?
Unfortunately, the research isn't so cut and dried.
While studies have confirmed that fasted cardio increase fat-oxidation rates in the short-term, long-term studies measuring actual fat-loss from fasted cardio have failed to find any real benefit.
If this seems confusing, that's because it is. But let me try to clear it up...
Just because something increases fat oxidation in the short-term doesn't automatically mean it's a viable fat-loss strategy in the long-term.
Fasted cardio may increase fat oxidation relative to fed cardio, but you can lose just as much fat with fed cardio.
It's not clear why fasted cardio doesn't seem to make a difference in the long-term, despite increasing fat oxidation in the short-term.
It may have something to do with the fact that eating prior to a workout increases excess post-exercise oxygen consumption (EPOC).
EPOC is a measure of oxygen intake following and is indicative of fat utilization.
The greater the EPOC, the more calories you burn around the clock, when you're not in the gym.
This could potentially explain why research has shown that fasted cardio isn't a more effective fat-loss strategy than the exact same cardio in a fed state.
Of course, that's just my theory, based on the research I've done. The truth is, nobody really knows why fasted cardio just isn't all it's cracked to be.
But the research is pretty clear that it's not.
The Problem(s) With Fasted Cardio
There are essentially two problems with fasted cardio that make a lot of people decide to avoid it.
- muscle-loss is accelerated during fasted cardio.
- you tend to perform worse than you would if you ate first.
Let's talk about each of these in a little more detail, shall we?
Fasted Cardio Breaks Down Muscle Faster
When you're in a fasted state, you're body may turn to fat for energy, but it also begins harvesting amino acids from muscle tissues to fulfill it's energy needs.
Compared to eating a nice carb-packed meal before you workout, you'll lose more muscle in a fasted state.
Luckily, this can be remedied, and we'll talk about how to do that in a little bit.
You Don't Perform As Well In A Fasted State
Research has shown that we tend to perform better when we've recently eaten and have high glycogen stores from which to draw energy.
You may notice that when you train fasted, you just don't hit the same numbers you hit after having eaten recently.
If you're training fasted, consuming carbs isn't an option because that would increase insulin levels and break the fast.
Luckily, this can be remedied as well...
Supplements That Can Help With Fasted Cardio
Fasted cardio on it's on is not a particularly effective fat-loss strategy and the downsides make it even less attractive.
Fortunately, there are a handful of supplements which can accelerate fat loss from fasted cardio while reducing muscle loss and improving performance.
So let's talk about some supplements that have actually been proven to work.
Supplements For Enhancing Fat-Burning
Supplements For Preserving Muscle
Supplements For Better Performance
When Is The Best Time To Do Fasted Cardio?
Most people find it easiest to do fasted cardio in the morning because you're naturally in a fasted state when you wake up.
You can do it later in the day, but that can be kind of excruciating, depending on how long you usually go without eating.
When I do fasted cardio (which is not often), it's first thing in the morning.
Ultimately, timing doesn't matter.
What To Eat After Fasted Cardio
The good thing about fasted cardio is that it enhances the anabolic response to post workout carbs and protein.
So it makes sense for your post fasted cardio meal to be high in carbs and high in protein.
Research shows that getting at least 40 grams of protein maximizes post exercise muscle protein synthesis, and since you're also in a state of glycogen depletion, it makes sense to load up on carbs too.
The Bottom Line On Fasted Cardio
Fasted cardio is far from the miracle fat-loss strategy it is often made out to be. It may increase fat oxidation in the short-term, but research has confirmed that it just doesn't add up to meaningful fat-loss in the long-term.
If you do want to give fasted cardio a chance, by all means, go ahead.
Just make sure you take the necessary measures to increase the upside (fat burning) while limiting the downside (muscle loss).
Matt Theis is the Co-Founder and CEO of Momentum Nutrition. Among other things, he is chiefly responsible for product formulation and has spent years researching, testing, and developing supplements.