Let’s get one thing straight right off the bat – fasted cardio is one of the hottest concepts in the fitness world right now. A quick look at Google trends will show just how popular this search term has become over the last couple of years. What started as an essentially non-existent concept in the mind of your average exercise back in 2012, is now one of the most searched fitness topics.
Every couple of weeks we’ll get a question about fasted cardio here on the blog.
“What is fasted cardio?”
“Is fasted cardio safe?”
“How do I do fasted cardio?”
I figured it’d make sense to put together a definitive guide for all of you who may be interested in fasted cardio and/or just want a little more information on what this training technique is all about. With that in mind, let’s get right into fasted cardio 101 and help you form a better opinion on whether or not it’s right for you.
The Science of Fasted Cardio
I know, I know….for a lot of you, this is the boring part. But unfortunately, to truly understand the nature of fasted cardio, we’ve got to talk about the biochemistry and physiology that’s going on inside of that body of yours. I promise I’ll keep this as brief as possible.
First things first, when you eat food, your body immediately begins to digest that food into smaller molecules. These molecules will be released into your bloodstream and used for a variety of processes within the cells of your body. A large proportion of the food you eat is going to be used for energy, also known as glucose (we’ll ignore ATP and the Krebs cycle today). When your body has glucose floating around, a biochemical pathway signals the release of insulin into your blood stream. Simply put, insulin helps get that glucose into the cells for energy or storage. Certain foods will raise insulin levels higher and faster than others, but our purposes, all foods are going to bump your insulin levels.
As the insulin is shuttling these molecules into cells, your body is in a “fed” and digesting state. Energy is readily available in this state. Once the molecules have all been used or stored, your insulin levels drop and you enter a “fasted” state. You bounce between fed and fasted states multiple times a day.
Now, when you’re in a fed state and you workout, your body is going to rely on the energy that’s already floating around your bloodstream. This makes sense – why work extra hard to release energy stores when perfectly good glucose is sitting right there for use? Not only that, insulin inhibits breakdown of fatty acids (which makes up body fat). Keep this is mind; you’re fighting an uphill battle every time you workout with high insulin levels.
On the flip side, when your body is in a fasted state, energy needs to be released from its stores. Your body has two choices – release energy from protein (muscle) or fat. Luckily for us, releasing energy from fat is more efficient, thus our body turns to our fat stores to meet the energy requirements of working out.
Things are starting to make more sense now, huh? When we’re working out after a meal, we’re burning the molecules we just ate and making a very small dent in the body fat we want to eliminate. When we workout in a fasted state, we’re burning right through body fat.
Getting into a Fasted State
A lot of people assume a fasted state simply means working out on an empty stomach. Unfortunately, it isn’t that simple. As I mentioned above, your insulin levels needs to be low to truly be working out in a fasted state. Depending on the foods you eat, your insulin levels could remain sky-high several hours after a meal.
This is why it’s so important to avoid the kinds of food that are especially effective at boosting insulin levels. Sugary foods, white flours, white rice are just some examples of foods to watch out for. But back on topic…
If you truly want to give fasted cardio a go, you’ve got to first make sure your diet is on point. All the fasted cardio in the world combined with a poor diet isn’t going to do much for your body fat. The basic science of fat loss is simple; burn more fat than you store. If you do this, you are 100% guaranteed to reduce inches, burn off body fat, and move closer to that lean, mean, athletic body so many of you are after.
Don’t take my word for it. Check out this peer-reviewed NIH study which examined the effects of pre-workout carbohydrate intake on lipolysis (fat loss). So to truly utilize fasted cardio, you’ve got to make sure your body is in a fasted state, which means habitually avoiding foods like the ones mentioned above AND making sure not to eat at least 90-120 minutes before a workout. The easiest solution to this is to do your cardio first thing in the morning when you’re absolutely in a fasted state.
Fasted Cardio and Trouble Areas
We should have a pretty good idea that fasted cardio is good for losing body fat, but I’ve got another wonderful little tidbit to drop on you – fasted cardio is particularly good at burning up the fat in those hard to hit areas. Everyone has that area on their body; for some it’s the belly, or thighs, or butt. No matter what you do, you just can’t seem to shed the body fat in that trouble area. Well, good news – fasted cardio is going to reduce your trouble areas faster too.
The reason for trouble areas is simple. Fat cells have two types of receptors on them; alpha and beta receptors. When activated, beta receptors speed up fat loss. Conversely, alpha receptors inhibit fat loss. Trouble areas are composed of fat cells with more alpha than beta receptors.
Not only that, trouble areas often have less blood flow to them. The chemicals which activate our fat cell receptors are thus hindered from getting to these trouble areas, thus leaving these trouble areas free from fat reduction. When your body is in a fasted state, there is an increase of blood flow to the abdominal region. Thus, those trouble areas in your midsection are going to be exposed to more of those fat-reducing chemicals found in your blood. Again, don’t take my word for it – check out the NIH study which details this process.
Using Fasted Cardio for Fat Loss
Hopefully you now have a better idea of what fasted cardio can do for your fat loss. To really crank things up a notch and give it a try, I’d recommend doing fasted cardio first thing in the morning. This way you know you’re truly in a fasted state. If you’re familiar with my blog, you also know I’m a big fan of HIIT cardio workouts. I’m talking short bursts of all-out intensity, rather than those long, slow, and boring jogs on the treadmill.
Just 15 minutes of alternated 30 second sprints can have massive effects on your body fat levels. The great thing is, you can knock out a serious fat-burning workout in 15-20 minutes, then get on with your day. If you’re also weight training (which you should be!), consider including your cardio AFTER hitting the weights to really speed up your fat loss.
The bottom line is this – you don’t HAVE to train in a fasted state to lose body fat. However, doing so is going to help speed up your progress, blast trouble areas more effectively, and ultimately deliver better results. Further, I’ve yet to see a study detailing any seriously negative consequences of fasted training, so in my opinion, there’s no risk of harm for training in this manner.
Get out there, give it a try, and as always, leave a message below if you have any comments, concerns, or questions about anything you read here.