Nowadays, getting up from the bed, drinking a glass of water, and then going out for a run becomes a Lifestyle statement. Every influencer and celebrity on social media is saying that the fasted cardio melts your fat faster. But what’s the reason behind this trend?
Now, to be honest, people love this method to save time. Because of a busy morning schedule, and at the same time they want to lose fat, they find this is a better option for them. The reason behind it is that, early in the morning when you get up from the bad, your insulin levels remain low, which gives your body the opportunity to use fat as an energy source.
Another aspect that makes this method famous is celebrity influence. Because when a fitness icon says I do fasted cardio, people take this as a secret formula. But it also has a scientific base that most people don’t know about.
And the main reason is fat loss. But there is a misunderstanding: “Working out on an empty stomach means muscle loss.” Well, it’s true that fasted cardio may break down your muscle for energy production. But it’s also true that, right time, proper intensity, and using the right method will not affect your muscles, but it will only target your fat cells.
What is Fasted Cardio?
Fasted cardio means you’re doing the exercise when your digestive system is not working. Which means your stomach is totally empty. Generally, it happens before breakfast when your body doesn’t have any glucose to use for energy production, instead of fat.
Let me give you a very easy example to understand. Suppose your house electricity has cut out, and your phone is almost dead. And what you have is just a powerbank, then you plug your phone into that device, and it directly gets charged by using that power. In the human body, the powerbank is your fat that your body stores for future energy reserve. When there is no glucose storage, the body shifts its power-generating process to fat.
Moreover, this process is totally different from the hormonal side angle. During fasted cardio, your body releases more growth hormone, which helps in the fat-burning process. You get better results with intermittent fasting, especially the 16-hour method. Because a very long time has passed since the last time you ate, and your body is already surviving. More importantly, this is the time when the body is highly responsive to trigger your fat.
Another interesting part is ‘Metabolic Flexibility. This means how easily your body can generate energy from fat. Those who always do fed exercise, their body become used to with glucose to generate energy. But fasted cardio teaches your body “how to survive without glucose.” And this helps in both weight control and insulin sensitivity in the long term.
Benefits of Fasted Cardio
1. Enhanced Fat Burn and Metabolism Boost
There is a distinct enzyme called Hormone Sensitive Lipase, in short ‘HSL’. This enzyme is activated during fasted cardio, and its duty is to break down fat cells to produce energy. This process is called Lipolysis
The HSL mostly activates when your insulin level stays low. And the environment sends your body a signal to burn fat. It’s like an emergency power mode when your body says, “There is no food out there, so run from the reserve.”
Also, fasted cardio sends such a signal to your brain so that it can start to quickly metabolize your fat. Because your body understands that I have activated its ‘effective mode’ when you’re on an empty stomach, so if you’re struggling with stubborn fat, fasted cardio might be a good solution for you.
2. Hormonal Balance and Improved Insulin Sensitivity
The big benefit of fasted cardio is that it doesn’t just burn fat, but also signals to your hormonal signal specialist, it improves your insulin sensitivity. As a result, Your Body Can quickly use glucose, which helps to prevent type to diabetes.
Moreover, fasted cardio helps to increase some other hormones like catecholamine, adrenaline, and noradrenaline. That means your body not only gets energy, but also keeps your mood well and improves your focus. after doing fasted cardio, so many people say that “I feel a type of mental clarity throughout the day.”
Also, fasted cardio keeps your cortisol and melatonin timing in check – that we call the circadian rhythm. Generally, cortisol remains high in the morning and melatonin at night. But those who have sleep problems or irregular routines, their hormonal balance messed up. Fasted cardio teaches your body a regular timing so that your sleep and wake-up cycle runs properly.
This hormonal balance keeps your body energetic throughout the day and also helps in the process of weight loss.
3. Mental Clarity and Increased Energy Levels
Fasted cardio doesn’t just burn fat; it also activates your brain. The main reason behind this is the brain-derived neurotrophic factor BDNF. It’s a kind of protein that makes your neurons stronger. In simple words, it’s a kind of brain fertilizers that create new cells and refresh the old.
Fasted cardio increases the BDNF production. As a result, it improves your focus and thinking power, and sometimes people say, ‘My head feels very light.’ This is called mental clarity.
Another interesting part is that exercising on an empty stomach increases stress
hormones, but not in a negative way. Rather, these hormones take your brain into ‘working mode,’ almost like preparing for a battle.
Generally, an empty stomach cardio performs better because at that moment our body isn’t busy with food, no digestion process, so the mind stays 100% clear.
That’s why some people like jogging early in the morning without breakfast, not just for fat loss but to get a mental edge throughout the day.
4. Convenience and Time Efficiency in Workout Routine
Morning shows the day. This saying goes 100% with fasted cardio. Because the two big advantages of exercising on an empty stomach,
- Saves time
- Mind and mood remain
Many people feel a heavy stomach after taking breakfast. And they also suffer from this dilemma: “I won’t get energy on an empty stomach.” But it’s not true, exercising without worrying about food means less decision fatigue.
And the saddest part is, most of the time our day starts with some unhealthy food. And it’s full of carbohydrates and some fried things. So, if you can make fasted cardio as a part of your routine, it will be a sustainable system to keep your glucose level, insulin levels, and your weight under control.
5. Improved Mitochondrial Function and Energy Production
Every cell has a powerhouse, which is ‘mitochondria.’ It’s the charging system in our body where we get energy. But if the powerhouse is weak, then we feel more fatigue, laziness, stamina a decrease.
Fasted cardio has a direct impact on your mitochondria. When your body burns fat instead of glucose, then energy is generated from a different path. And this path increases the efficiency of mitochondria.
Research also shows that fasted cardio helps in increasing the amount of mitochondria, which is called mitochondrial biogenesis. As a result, it builds up your energy and at the same time your endurance.
It’s similar to – after charging your mobile once, it lasts for a day. Now, it’s lasting for 2 days. Which means it doesn’t keep your weight in check by just metabolizing your fat, but also strengthens your inner powerplant.
Downsides
1. Muscle Loss and Decreased Strength
The biggest fear of fasted cardio among people is muscle loss. And it’s true that cardio has a catabolic state if it’s not performed with the right intensity. It happens because when your glucose has run out, it starts tapping on fat cells, but in extreme deficiency, it starts breaking down your protein cells.
This protein directly comes from our muscles. In simple words, it converts your muscle into energy.
Doing fasted cardio once or twice a week doesn’t do much harm. But if you’re doing this every day with high intensity, in a fasted state, without taking proper nutrition, then it may affect your muscles.
Fasted state
- Reduce strength
- Require more time to recover
- Lose muscle mass and body structure.
However, there are some ways to avoid this,
- Taking EAA (Essential Amino Acids) or BCAA before fasted cardio will prevent muscle breakdown
- Doing low-intensity cardio during the fasted state instead of intense, like HIIT, will preserve your muscle.
- And not overdoing this more than twice a week is the smartest approach.
2. Hypoglycemia (Low Blood Sugar) and Side Effects
I would recommend staying away from fasted cardio if you have a low blood sugar problem. But you’re already in a low glucose state in the morning. And exercise may take you to more lower state. As a result, your body won’t be able to handle the situation, and you’ll feel
- Sudden dizziness
- Shaking hands
- Feeling weak
- Blurred vision
- Feeling nauseous
And if the condition gets worse, you might be admitted to the hospital.
When the body’s blood sugar is lowered significantly, then your brain struggles to function. Because glucose is the primary fuel for your brain. And it will disturb your focus, decision-making power, and even your balance.
To prevent these problems,
- Don’t start with completely empty. Instead, drink some water and electrolytes.
- Keep the intensity moderate.
- Always listen to the signals. If you feel dizzy, stop immediately.
- Avoid cardio if the morning is extreme heat or humidity.
3. Hormonal Imbalance and Increased Stress Hormones
Fasted cardio builds up the cortisol level. This stress hormone increases the tendency of fat accumulation in the human body. The most dangerous part is, if the hormone stays for a long and you’re practicing the process for a long time, it will reduce the effectiveness of your immune system, build up inflammation, and also cause muscle loss.
Research from Harvard Medical School also shows that a high amount of cortisol slows down the metabolic process and increases body fat, especially around the abdominal area. As a result, it can disbalance your hormonal profile.
On the other hand, it can also disturb the thyroid hormone production, like T3 and T4. Because the body starts conserving energy to survive. Also, it reduces the basal metabolic rate (BMR), and you face difficulty keeping weight under control.
Who needs to avoid fasted cardio?
- Those who are suffering from PCOS and hypothyroidism.
- Chronic stress and adrenal fatigue problems
- Pregnant woman
- Hypertension and Diabetic patients.
- If a woman has an irregular menstrual cycle, fasted cardio can further increase the hormonal disturbance.
Another important thing our cortisol level naturally remains high after we wake up and it takes some hours to get back into the normal state. Also, fasted cardio increases the amount, and it may turn into something bad anytime.
Especially for women, because according to the Women’s Health Initiative report, cutting out calories and doing fasted cardio at the same time can disturb the estrogen balance. This can have a very harmful impact on bone health and also the overall hormonal balance.
4. Long-term Metabolic Rate Decline
If you stay on an empty stomach for a long time and at the same time you go for exercise, your body considers this a threat. As a result, it activates its survival mode. Which means it reduces your BMR, then your body uses fewer calories to survive, and it reduces the speed of your fat loss.
In this situation, if someone doesn’t fully recover or continue fasted cardio, then the person may face overtraining syndrome. And this will cause sleep problems, injury, fatigue, stress, and hormonal imbalance.
Plus, research shows that doing fasted cardio more than 3-4 days a week can drop your metabolism rate. In the long term, it reduces muscle retention
How to control,
- Re-feed or High-calorie day at least 2-3 days a week.
- During fasted cardio, keep 2 rest days.
- Take enough protein to prevent muscle loss.
- Don’t go for HIIT. Instead, do low to moderate intensity steady state cardio (LISS)
5. Performance Drop and Fatigue
It’s very common, especially at the beginning phrase. You’ll notice a lack of energy and also dizziness. It happens because when you’re on an empty stomach and doing any activity, your body can’t generate enough ATP to supply. As a result, your muscles face difficulties to work in your favor.
Also, you become mentally weak due to low glucose and ATP production. And it negatively affects your focus, also fades your motivation and excitement halfway through. Plus, your recovery process also slows down, and you can’t give your 100% focus and performance to your next session.
Recognize Your Body’s Signal Before Fasted Cardio
The first thing you need to consider before starting fasted cardio is, listen to your body. We often force our body to run and ignore these symptoms, like dizziness, weakness, diarrhea, or excessive fatigue. These are some alarming signs that are trying to say that “I’m not ready yet.”
Along with these, there are two more things that you also have to consider. Your heart rate variability (HRV) and blood sugar monitoring. In this modern era, this is now very easy to know with your smartwatch and a little blood sugar meter.
These two metrics help to know about your stress and energy level. If the HRV shows too low, and blood sugar looks irregular, then avoiding fasted cardio will be a smarter option.
The Bottom Line
Fasted cardio is beneficial if you know how to do that without overwhelming the process. Unless it brings trouble, and if the condition gets out of control you may need to be hospitalized. That’s why you need to follow the SMART technique, which means a technique that is Specific, Measurable, Achievable, Relevant, and Time-bound.
If needed, add fed cardio to your routine. Also, keep a healthy diet, enough protein intake, and hydration. Most importantly, if you decide to go fasted, then always start slow. You can start with brisk walking, or if you think you have more stamina, then start with moderate speed jogging.
And finally, fasted cardio can be a powerful tool, but only then, when you are smart, aware, and listen to your body to make the right decision. So first, know yourself, make a proper plan, and add this a part of your regular activity to see real results.
