What is Fasted Cardio?

Fitness enthusiasts and professional athletes widely praise fasted cardio as an effective strategy to maximize fat loss and improve overall health. Fasted cardio refers to performing cardiovascular exercise, such as running or cycling, in a fasted state, which means not consuming food or calories for an extended period, typically around 8-12 hours, before the workout. During this time, fat stores are primarily used for energy as glycogen levels are depleted. Let’s dig into the benefits of fasted cardio!

The Science Behind the Benefits of Fasted Cardio

The concept of fasted cardio is based on the utilization of different energy sources by our bodies during exercise. When food is consumed, carbohydrates are broken down into glucose, which is subsequently stored in the liver and muscles as glycogen. During exercise, our bodies use glycogen first as a primary fuel source, followed by fat.

In a fasted state, glycogen stores are depleted, resulting in a shift towards using fat as the primary source of fuel in our bodies. This is the main reason why fasted cardio is considered effective for maximizing fat loss. This article will explore the benefits of fasted cardio and ways to incorporate it into your workout routine for optimal fat loss by delving into the scientific evidence supporting its benefits.

Fat Oxidation and Lipolysis

Studies indicate that fasted cardio increases fat oxidation by making the body more efficient at using stored fat as fuel. This is achieved by increasing the rate of lipolysis, which is the process of breaking down triglycerides (stored fats) into free fatty acids and glycerol.

Performing cardio in a fasted state results in low insulin levels and elevated levels of hormones such as cortisol, growth hormone, and norepinephrine. These hormonal changes stimulate lipolysis and promote the release of free fatty acids into the bloodstream, allowing them to be utilized as an energy source during exercise.

One study in the Journal of Applied Physiology found that fasted cardio led to a 20% increase in fat oxidation compared to fed cardio. Another study published in the British Journal of Nutrition demonstrated that participants who did fasted cardio burned nearly 20% more fat than those who ate before exercising.

This man is clearly experiencing the benefits of fasted cardio!

Enhanced Mitochondrial Function Benefits of Fasted Cardio

Fasted cardio can also lead to enhanced mitochondrial function, which plays a crucial role in energy production and overall cellular health. Mitochondria are the “powerhouses” of our cells, responsible for generating the energy required for various cellular processes.

Training in a fasted state can stimulate mitochondrial biogenesis – the process of creating new mitochondria – and improve their efficiency in utilizing fatty acids for energy production. A study published in the Journal of Physiology found that fasted cardio increased mitochondrial content and function, leading to improved endurance capacity.

Adaptive Responses

Fasted cardio can also promote various adaptive responses within the body that contribute to the overall benefits. For example, exercising in a fasted state can increase the expression of genes responsible for fat metabolism, enhancing the body’s ability to break down and utilize fat for energy. Moreover, fasted cardio can stimulate the production of heat-shock proteins, which are responsible for cellular repair and protection against stress-induced damage.

In summary, the science behind the benefits of fasted cardio lies in the body’s ability to adapt to using fat as a primary energy source, leading to increased fat oxidation, lipolysis, and enhanced mitochondrial function. These adaptive responses contribute to the overall effectiveness of fasted cardio in maximizing fat loss and improving overall health.

Benefits of Fasted Cardio: Improved Fat Loss

One of the most significant benefits of fasted cardio is the potential for improved fat loss. As we have discussed, exercising in a fasted state allows the body to rely more on stored fat for energy, which can result in increased fat oxidation and help you shed those stubborn pounds. Let’s explore the various ways fasted cardio can contribute to improved fat loss:

Targeting Stubborn Fat

This is probably everyone’s favorite of the benefits of fasted cardio! Stubborn fat refers to fat deposits that are difficult to lose and are commonly found in areas like the lower abdomen, hips, and thighs. These areas have a higher concentration of alpha-2 adrenergic receptors that can slow down the rate of lipolysis. However, during fasted cardio, the levels of catecholamines such as adrenaline and norepinephrine increase, which help counteract the effects of alpha-2 adrenergic receptors and increase the rate of lipolysis in these stubborn areas.

Optimizing Fat Burning Hormones

Fasted cardio can optimize the production of fat-burning hormones, such as human growth hormone (HGH) and adiponectin. HGH is a hormone that plays a significant role in fat metabolism and muscle growth. Studies have shown that exercising in a fasted state can increase the production of HGH, leading to greater fat loss and muscle preservation. Fat cells release adiponectin, a hormone that enhances the body’s ability to break down and utilize fat for energy. Studies show that fasted cardio increases adiponectin levels, which further promotes fat loss.

Improving Insulin Sensitivity

Insulin sensitivity refers to how effectively our cells respond to insulin, a hormone responsible for regulating blood sugar levels. When insulin sensitivity is high, our cells can efficiently absorb glucose from the bloodstream, reducing the likelihood of storing excess glucose as fat. Studies have shown that fasted cardio improves insulin sensitivity, which can regulate blood sugar levels and decrease fat storage, promoting fat loss.

Post-Exercise Caloric Burn

Another way that fasted cardio contributes to improved fat loss is through increased post-exercise oxygen consumption (EPOC), also known as the “afterburn effect.” EPOC refers to the number of calories burned after exercise as the body recovers and returns to its resting state. Studies have shown that fasted cardio can result in a higher EPOC, meaning you’ll continue to burn calories even after your workout is complete.

In conclusion, fasted cardio can lead to improved fat loss through various mechanisms, such as targeting stubborn fat, optimizing fat-burning hormones, improving insulin sensitivity, and increasing post-exercise caloric burn. By incorporating fasted cardio into your workout routine, you can maximize these benefits and reach your weight loss goals more effectively.

How to Incorporate Fasted Cardio Into Your Routine

Incorporating fasted cardio into your workout routine can help you maximize fat loss and improve overall health. However, it’s essential to approach it safely and effectively. Here are some tips on how to introduce fasted cardio into your fitness regimen:

Choose the Right Time of Day

The best time to perform fasted cardio is typically in the morning before breakfast. This ensures that you have gone an adequate amount of time without consuming any food, allowing your body to enter a fasted state. However, if morning workouts don’t fit your schedule, you can also consider doing fasted cardio after an extended period without food, such as in the late afternoon or evening, at least 4-6 hours after your last meal.

Select the Appropriate Cardio Exercise

Do fasted cardio using various types of cardiovascular exercises, such as walking, jogging, cycling, swimming, or using an elliptical machine. The most important thing is to choose an exercise that you enjoy and can perform consistently. When starting, opt for low to moderate-intensity workouts, as high-intensity exercises may cause lightheadedness or fatigue in a fasted state.

Gradually Increase Duration and Intensity

When you first begin fasted cardio, start with shorter sessions (around 20-30 minutes) and gradually increase the duration as your body adapts. As you become more accustomed to fasted cardio, you can also slowly increase the intensity of your workouts. However, always listen to your body and avoid pushing yourself too hard, as this can increase the risk of injury or burnout.

Combine the Benefits of Fasted Cardio with Strength Training

For optimal results, consider joining fasted cardio with strength training exercises. This can help you maintain or build lean muscle mass while also losing fat. Perform strength training exercises after your fasted cardio session or on other days to ensure your muscles have enough time to recover.

Monitor Your Progress and Adjust Your Routine

Keep track of your progress by recording your workout, including the length, intensity, and type of exercise. Regularly assess your progress by measuring your body composition, weight, and overall fitness level. Based on your results, adjust your routine as needed to continue making progress towards your goals.

Conclusion: Embrace the Hangry Runner Within

By having fasted cardio into your workout routine, you’ll not only be giving your body a fat burning boost but also channeling your inner hangry runner. Just imagine the satisfaction you’ll feel when you can finally say, “I conquered the treadmill on an empty stomach, and I lived to tell the tale!”

Fasted cardio can provide a unique and effective way to lose fat and improve your overall fitness. Just remember to approach it with caution, listen to your body, and always refuel post workout (because nobody likes a hangry athlete). So go ahead, embrace the fasted cardio lifestyle, and let the fat loss and the (slightly grumbly) good times roll!

More from Vibing Vitality:


  1. Villareal, D. T., Smith, G. I., Sinacore, D. R., Shah, K., Mittendorfer, B. (2019). Regular Multicomponent Exercise Increases Physical Fitness but Not Serum Adiponectin or Insulin in Obese Postmenopausal Women. Journal of Aging Research, 2019, 1-8. doi: 10.1155/2019/9891704
  2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3069710/
  3. Schoenfeld, B. J., Aragon, A. A. (2018). Is Cardio Necessary for Fat Loss? Journal of Strength and Conditioning Research, 32(6), 1555-1563. doi: 10.1519/JSC.0000000000002430

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