We all know that working out can help you lose weight. But there is one thing that can help you lose weight even faster, and that’s eating less. So what’s the best way to do that?
If you’re like most people, eating less means feeling hungry all the time—and that means it’s hard to stick with it. That’s where an empty stomach workout comes in! By doing this kind of workout, which involves burning fat for energy instead of glycogen (carbs), you’ll be able to eat less without feeling hungry or getting tired from muscle depletion. This will allow you to lose weight more quickly than if you weren’t exercising at all.
And because your body is using fat as its primary source of fuel instead of carbs, it will also help keep your metabolism running strong so that your body burns calories more efficiently throughout the day.
Right here on Buy and Slay, you are privy to a litany of relevant information on empty stomach workout benefits, cardio on an empty stomach, and so much more. Take out time to visit our catalog for more information on similar topics.
Empty Stomach Workout For Weight Loss
If you’re familiar with intermittent fasting then fasted cardio is something you may be doing already.
However, if you’re not then let me explain.
Fasted cardio is when you do exercise in a completely fasted state to help burn fat.
It’s not essential for fat loss and you can get lean without doing it. However, there is some evidence that shows you may be able to get leaner, faster using fasted cardio.
Additionally, when done properly fasted cardio can also help you lose more stubborn body fat. Which is useful for anyone who struggles to lose that last bit of fat from their abs and love handles i.e. most people.
However, as great as this potentially sounds it’s not all sunshine runs and fat loss. If you do it wrong you can end up losing muscle mass as well as fat.
In this article, we’ll explore the pros and cons of fasted cardio as well as how to do it for the best results.
Let’s begin.
How Fat Loss Works (A Quick Recap)
When it comes to losing fat, your diet is the single most important factor, and this is because of the energy balance equation.
The energy balance equation has 3 irrefutable rules which are as follows;
- To lose weight you must be in a calorie deficit = eating fewer calories than you need
- To maintain weight, you must be in a calorie balance = eating the calories you need
- To gain weight you must be in a calorie surplus = eating more calories than you need
You will always be in one of these states, which means to lose weight you must create and maintain a calorie deficit.
This is important because doing cardio whether it’s fasted or fed can help you create and maintain a calorie deficit but only if your diet is in order.
No amount of exercise can help you reach your fat loss goals if you’re not eating the right number of calories and getting the right macronutrients.
What is Fasted Cardio?
Put simply fasted cardio is doing exercise in a completely fasted state.
This is generally 8–12 hours after your last meal when your body insulin levels are back at base levels and you’re no longer digesting food
Anything other than this is consider fed cardio and the difference between the 2 is how your body uses energy.
When doing fed cardio your body draws on the food you most recently ate to provide the energy you need, whereas when you’re in a fasted state your body draws on stored fat and glycogen for the energy it needs.
The Benefits of Fasted Cardio?
Fasted cardio has some unique benefits that you don’t necessarily get when training in a fed state. Research shows that exercising when fasted increases the rates of 2 processes that are important to fat loss; lipolysis and fat oxidation.
Lipolysis is the name given to the breaking down of fat for energy
Fat oxidation is the burning of this energy by your body
What this means is that when you exercise in a fasted state your body becomes more efficient at mobilising and then burning fat compared to exercising in a fasted state.
Additionally, and quite importantly, there is evidence showing that when you’re in a fasted state blood flow to your stomach is increased. This is good news as increased blood flow to this area translates to more fat burning chemicals reaching there and more total fat loss as a result.
In short, fasted cardio can help you burn more fat, particularly stubborn fat like that around the hips and stomach.
In fact, some research shows that fasted cardio may burn up to 20% more body fat than non-fasted cardio with additional studies showing that whilst fasted cardio has no benefits for total weight loss when compared to fed cardio it does help participants burn more fat.
What this means is you can get lean with both fasted and fed cardio but doing fasted cardio will help you improve body composition faster as you lose more body fat.
The Disadvantages of Fasted Cardio
Ok, so we know the benefits of doing fasted cardio but what are the disadvantages.
The main one is the increase in muscle breakdown rates associated with training in a fasted state. Sure, the effects aren’t going to massive but due to the fact it can be difficult to build muscle for lots of people, it can be enough to matter.
This becomes an issue when your body cannot keep up with the amount of repair your body needs as a result of the damage and break down from training.
Now, don’t get me wrong muscle damage and break down from training is a normal process, the difference is when you’re in a fasted state your body doesn’t have the nutrients it needs to keep up with the repairs it needs to do.
Over time this could result in less muscle growth or even muscle loss.
In addition to this, you may find that when you first switch to fasted cardio your workouts lack their usual intensity. Again, this is a normal part of training fasted and most people will find their energy and focus is lower when they first switch over.
This means whilst fasted cardio can help you lose fat, particularly stubborn fat, it also has some potential downsides that you need to be aware of.
After the first couple of weeks, you will adjust and things should go back to normal. You just have to accept the initial dip in performance and be willing to wait it out.
What About Fasting & Weightlifting?
When it comes to fasting and weightlifting, it can also be just as effective as fasted cardio at burning stubborn body fat by ramping up the production of fat-burning chemicals in your body.
However, like with doing fasted cardio, it’s normal to see a drop in strength for the first few weeks as your body adjusts to training in a fasted state. This is only temporary and is the result of having less muscle glycogen to fuel your workouts.
You see carbs improve workout performance and by taking them away you lose the performance benefits they give you.
There is research showing that your body can adapt to training in a fasted state and use your glycogen stores more efficiently, but you may find that your fasted workouts are never quite as good as your fed workouts.
For this reason, you may want to do fasted cardio but stick to doing your weightlifting in a fed state like normal, particularly if you have body composition goals that include building or maintaining muscle.
How to Do Fasted Cardio
As we touched on earlier fasted cardio is not much better at burning fat when compared to fed cardio, which is why the type of cardio you do matters.
When it comes to doing fasted cardio you really want to do high-intensity interval training (HIIT) to get the best results.
This particularly important the leaner you get and the more stubborn fat you have to lose.
This is primarily because HIIT when compared to steady-state cardio, not only burns more calories but does it in less time.
For example, in one study 2 groups were compared;
- Group 1: did 4–6 30 second sprints with a 4-minute rest in between
- Group 2: did 60 minutes of incline treadmill walking
At the end of the study, they found that the sprint group lost more fat. Not only this but they did it in a fraction of the time.
In addition, HIIT also;
- Increases your metabolism for up to 24 hours
- Improves insulin sensitivity which helps your body use what you eat more efficiently
- Increase your body’s ability to burn fat (fat oxidation)
- Increases fat mobilisation (lipolysis)
- Elevates growth hormone levels in the body
- Reduces hunger after exercise which helps reduce total daily calorie intake
It’s clear for all to see that if you’re only going to do a small amount of cardio per week then HIIT is the way to go for a maximum return on your effort.
Add to this the fact that when you do it in a fasted state these effects are amplified and it’s a no brainer.
How to do it:
- Do 2–3 cardio sessions per week
- Train after lifting weights or on rest days
- Do HIIT training — sprints on a treadmill or bike are ideal
- Train first thing in the morning when you’re naturally in a fasted state
Just in case you were thinking of doing steady-state cardio for your fasted training, note that prolonged bouts of exercise in a fasted state have been shown to increase the breakdown of muscle protein putting you at a greater risk of losing fat and muscle.
Play it smart and stick with HIIT training or eat first if you want to do longer duration bouts of cardio.
When to Do Fasted Cardio
I know I just answered this question, but I wanted to go into a little more detail to show you why it’s best to do your fasted cardio first thing in the morning.
Ok, so let’s say that you eat dinner between 6–8 pm and you don’t eat again that day, then when you wake up the next morning your insulin will be at baseline levels.
Additionally, research shows that fat oxidation rates are highest 6+ into your fast and because you’ve spent the night asleep you can guarantee you’ll be in a fasted state.
Remember, this is important because eating elevates your insulin levels and puts you into a fed state. When you’re in a fed state you don’t get the benefits of increased fat mobilisation and fat burning.
This means you’re in the perfect position to get out there and do some fasted cardio, no additional preparation required. No wonder doing fasted cardio first thing in the morning is so popular.
For most people, the difficulty of managing their meals in a way that allows them to train fasted in the afternoon or evening is too difficult when balancing work, family and everything else.
Now, this doesn’t mean you can’t do fasted cardio later in the day, but it does make it trickier to pull off.
Firstly, if you’re going to fast until the afternoon and then workout you may very well find that your performance deteriorates as you get further through your day and deeper into your fast.
Secondly, if you’re going to eat during the first part of the day and aim to get back into a fasted state for the afternoon or evening this requires careful planning as even have a small amount of sugar or serving of whey protein is enough to raise your insulin levels for a number of hours.
Remember, that whilst fasted cardio can offer a few benefits for those looking to lose that stubborn fat it is no necessary and if you can’t make it work then don’t feel like you have to force it.
Should You Eat After Doing Fasted Cardio?
This is a popular question particularly amongst those following an intermittent fasting protocol.
The short answer is yes.
You should eat after you’ve done your fasted cardio and the primary reason for this is preventing the increase in muscle breakdown that occurs after fasted training.
Sure, technically speaking you could eke out a little more fat loss if you held off eating for a while but for most people, the risk of losing muscle mass isn’t worth the small increase in fat gain they might receive.
This is important as if you remember from earlier the biggest downside of fasted training is potential muscle loss.
By breaking your fast after your workout, you help to negate this and make fasted training more effective.
Summing Up
Fasted cardio is the name given to any exercise done when in a completely fasted state i.e. when your body is no longer digesting food and your insulin levels, are at baseline.
When done correctly it can not only help you lose more fat, but it can specifically help you lose the last bits of stubborn fat that most people struggle with. However, when done incorrectly it can cause muscle loss and skinny fat syndrome.
To do it right you want to keep cardio to 2–3 sessions a week, either after your weightlifting or on rest days and do some form of HIIT like sprints.
Aim to workout first thing in the morning and eat a mix of protein and carbohydrates once you’ve finished.
Empty Stomach Workout Benefits
There are several potential benefits of running on an empty stomach, let’s check them out!
#1: It May Increase Fat Burning
Fasted cardio has been shown to increase the relative percentage of fat oxidation, meaning that more of the calories you burn during the workout come from stored body fat.
When you exercise, the body uses stored fuel for energy. Carbohydrates are stored as glycogen, fat is stored as triglycerides in fat tissue, and protein forms structural proteins in muscle.
The body has limited glycogen stores in the liver and skeletal muscles, and these levels deplete overnight during your fast. Therefore, when you do fasted cardio, a greater percentage of the energy to support your workout comes from oxidizing fat. In fact, some studies show you may burn up to 20% more fat when exercising on an empty stomach.
That said, while a fasted workout can increase fat burning, it also increases muscle-burning because the body also turns to metabolizing the protein in muscle for energy as well.
Additionally, it’s important to note that the calorie expenditure does not increase during a fasted workout; rather the substrate, or source, of the calories to burn shifts.
#2: It May Contribute to Greater Weight Loss
Although fasted cardio doesn’t burn more calories, some studies have shown that people who exercise on an empty stomach end up eating fewer calories throughout the day.
Since weight loss results from a caloric deficit, it is possible that the reduced caloric intake in a fasted cardio state can yield more weight loss if it indeed contributes to less energy intake throughout the day.
#3: It Can Reduce Digestive Distress
Some people simply feel better working out on an empty stomach. Runners with sensitive stomachs, for example, often find that running on an empty stomach prevents cramping, gas, diarrhea, and bloating.
For some runners, even small snacks can cause side stitches and the need to quickly find a bathroom mid-run. In these cases, fasted workouts may be preferable.
#4: It May Improve Blood Sugar Control
The most common concern about doing fasted cardio is hypoglycemia, or low blood sugar, but most studies show that it does not cause detrimental decreases in blood sugar, even for those with diabetes.
Some studies have even found positive effects on blood sugar regulation and insulin sensitivity from exercising on an empty stomach. However, if you have diabetes, you should consult your healthcare provider before starting a fasted cardio routine.
#5: It Can Be Energizing
Just as some people feel depleted and exhausted if they try to exercise on an empty stomach, some people find they feel more energized.
Moreover, since fasted cardio usually takes place first thing in the morning, some proponents of working out on an empty stomach say it helps them jumpstart the day, and they finish the workout feeling like they are ready to go.
5 Drawbacks Of Fasted Cardio
Fasted cardio isn’t without its drawbacks, including the following:
#1: It Does Not Lead to More Fat Loss
Even though doing fasted cardio may help you burn a higher percentage of calories from fat, it does not seem to lead to greater fat loss or favorable changes in body composition.
According to research, fat loss and body composition changes were the same whether cardio exercise is performed in the fed or fasted state.
#2: It Can Increase Cortisol Levels
Cortisol is one of the primary stress hormones in the body, and chronically elevated cortisol levels have been associated with triggering the body to store more fat, particularly in the abdominal area.
Studies have shown that working out on an empty stomach can increase cortisol levels, as the body perceives fasted cardio as a significant physiological stressor.
#3: It May Cause Hormonal Imbalances
Just as doing fasted cardio can alter normal cortisol secretion, there is also evidence to suggest that exercising in the fasted state can cause hormonal abnormalities. This can potentially increase the risk of injury.
#4: It May Be Detrimental to Muscle Mass
As mentioned, working out in a fasted state can force your body to burn protein in muscle tissue for energy, which is detrimental to strength, athletic performance, health, and metabolic rate.
#5: Performance May Suffer
Arguably the biggest problem with fasted cardio is that most research shows athletic performance suffers when you exercise without adequate fuel. Strength, speed, and intensity levels tend to be significantly better when exercise is performed in a fed state, particularly when adequate carbohydrates are available.
The rate of perceived exertion also tends to be higher with fasted cardio, meaning the workout feels harder than it actually is.
The Pros And Cons Of Fasted Cardio: Should You Exercise On An Empty Stomach?
Taken together, these findings suggest that while there are several pros and cons to consider, most people running on an empty stomach or doing some other form of fasted cardio will lead to subpar performance. Over time, if you regularly engage in fasted workouts, you may limit your fitness progress.
At the end of the day, deciding whether or not you should workout on an empty stomach depends on your goals, motivations, and what works for your body.
The primary reason to decide to do fasted workouts would be if you really struggle with GI upset if you exercise after eating. However, most coaches say that the digestive tract is somewhat trainable.
Try very light, easily digestible snacks like rice cakes, a few bites of an energy bar, or a couple of dried dates or apricots two hours before a run. If that seems tolerable, gradually move the window to 90 minutes before the run and see if your body feels better.
Cardio On An Empty Stomach
Whether cardio on an empty stomach can speed up fat loss is a commonly debated fitness topic. Some believe fasted cardio is more effective at burning fat while others believe it can decrease performance and limit fat loss.
Who is right? The following will inform you of what research has to say about the topic and offer compelling reasons why fueled exercise leads to greater overall fat burn.
Cardio on an Empty Stomach Burns More Fat DURING Exercise
Two fuel sources—carbs & fats—are used to generate energy for muscle contraction during exercise. For endurance exercise performed at a moderate intensity, you obtain 50–60% of energy needed from glycogen (which is stored energy from carbs) and the rest from fats.
When you deplete glycogen stores by fasting overnight, or going several hours without refueling, fatty acids break down in the mitochondria to be used as a secondary energy source. As workout intensity increases, your reliance on carbohydrates increases as well.
In one study that tested the fat burning effect cardio on an empty stomach, six healthy men cycled for 60 minutes at a low to moderate intensity:
Group 1– Fasted overnight before the bike ride.
Group 2– Performed the bike ride after ingesting 0.8g/kg of glucose or fructose to replenish glycogen levels 1 hour prior to the workout.
Results: After 20-30 minutes of exercise, the rate of fat burn was higher in the fasted group than in the glucose or fructose group. This trend continued throughout 50-60 minutes of exercise. There was also a higher quantity of FFAs (Free flowing fatty acids) available in the blood in a fasted state throughout the exercise.
The Take Away: This particular study suggests that more fat was burned by the group that performed MODERATE activity on an empty stomach… DURING THE EXERCISE ITSELF.
But Empty Stomach Cardio Does Not Burn More TOTAL Fat
Not so fast. Notice how “moderate” exercise is emphasized in the example above? Research shows that people who burn fat during their workouts actually burn less fat the rest of the day. Overtime, fat burning is not an immediate process, rather, it occurs over the course of, not a few hours, but a few days.
As you burn more carbohydrates during your workout, the body will burn more fat post exercise. This “afterburn effect” where your metabolism is elevated for several hours or days following your workout is critical when debating the benefits of fasted cardio.
While you may burn more fat during your workout on an empty stomach, your overall workout intensity may decline. Your body’s ability to burn fat post-exercise is compromised. Consider the whole 24 hour period and cardio on an empty stomach is less effective.
Evidence supporting fueled exercise
Researchers from Italy investigated the contrasting reports on whether training in a fasting condition enhances weight loss. There were 8 healthy young men who performed early morning slow cardio under 2 conditions:Adaptations to skeletal muscle with endurance exercise training in the acutely fed versus overnight-fasted state.
1. Empty stomach
2. After eating
Eating increased both oxygen consumption (VO2) and respiratory exchange ratio (RER) significantly, 12 hours after the cardio, VO2 was still higher for the group who had eaten, although RER was significantly lower in the FED test, indicating greater fat burn.
The group that ate before the cardio session continued to burn significantly more calories up to 24 hours after the exercise bout. The authors concluded that “when moderate endurance exercise is done to lose body fat, fasting before exercise does not enhance lipid utilization (fat loss); rather, physical activity after a light meal is advisable.” Check out this article for more on pre-workout meal ideas.
High Intensity Cardio on an Empty Stomach Can Burn You Out
During intense exercise that approaches your maximum effort, most of your energy comes from glycogen. If you deplete your glycogen stores, you compromise your energy output. As glycogen stores in the muscles and liver are depleted, and the blood glucose level begins to fall, fatigue, lack of coordination, light-headedness and lack of concentration can occur. Commonly known as “hitting the wall” or “bonking,” fat simply can’t be metabolized fast enough to support the higher pace, so you slow down or even stop.
While research and studies are still ongoing, there are a few certainties. Steady state fasted cardio might burn more fat during your workout, but your post-workout fat burn is compromised. When performing high intensity cardio and exercises, glycogen levels need to be restored to achieve optimal performance and results. Doing cardio on an empty stomach if you aren’t able to sustain adequate energy levels, your workout will suffer.
Always choose energy and sustainability over anything else! Even early in the morning, grab a protein shake, piece of fruit, or handful of trail mix, to help your body to use efficient energy sources to power your workout.
