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Fasted Cardio: Does It Really Accelerate Fat Loss?



Well-known member
Aug 7, 2023
Are you tired of struggling to lose those stubborn pounds? Many individuals are constantly seeking ways to accelerate their fat loss journey. One method that often piques interest is fast cardio. But what exactly is fasted cardio, and does it hold the key to faster fat loss?

Fasted cardio refers to exercising cardiovascular on an empty stomach, typically in the morning before breakfast. The idea behind fasted cardio is that by exercising fasted, your body will tap into fat stores more readily for energy since glycogen levels are lower after an overnight fast.

This article delves into the potential benefits, considerations, and best practices surrounding fasted cardio, helping you decide if it fits your fitness journey.

How Fasted Cardio Influences Fat Burning​

The foundation of fasted cardio lies in glycogen depletion. Glycogen is the stored form of glucose in the muscles and liver, serving as a primary energy source during physical activity. When we engage in overnight fasting, glycogen stores gradually diminish as the body utilizes these reserves to maintain essential bodily functions during the fasting period.

The body enters a metabolic state called ketosis with prolonged fasting exceeding 12-16 hours. In this state, it starts producing ketone bodies, alternative energy sources derived from fat breakdown. While fasted cardio may not necessarily induce ketosis, it can contribute to entering this state faster, potentially further promoting fat utilization.

Some studies suggest it also elevates your metabolic rate, increasing calorie burning throughout the day. According to other studies, exercising in a fasted state may lead to increased post-exercise oxygen consumption (EPOC). The body continues to burn calories at an elevated rate after the workout, contributing to overall energy expenditure.
fasted cardio

The Research: Does the Science Support It?​

A recent study by the Journal of Exercise and Fitness showed that 30 overweight and obese young adults reduced their BMI, body fat percentage, and weight after six weeks of fasted aerobic exercise. The research suggested that exercising on an empty stomach may promote using fat stores for energy.

However, research published in the Journal of Obesity & Metabolism in Clinical Nutrition in 2014 compared the effects of fasted and fed cardio on weight loss over eight weeks. It highlights the complex interplay of factors that influence weight loss, with factors like diet and total calorie expenditure playing a more significant role in the long run.

Fitness level, dietary habits, and workout intensity affect how your body responds to this approach. Individuals with higher fitness levels may experience a more pronounced increase in fat burning during fasted exercise. Additionally, those following a low-carbohydrate diet might find fasted cardio more beneficial, as they already have depleted glycogen stores.

Pros and Cons of Fasted Cardio​


During fasted exercise, your body depletes glycogen stores, forcing it to tap into stored fat for fuel. It may also improve insulin sensitivity, benefiting overall metabolic health. Additionally, this can be beneficial for individuals with prediabetes or type 2 diabetes.

Fasted cardio can be a practical option for individuals who prefer to exercise in the morning or find it more convenient to work out on an empty stomach. It eliminates the need to plan and prepare a pre-workout meal, making the fitness routine more accessible and time-efficient.


Fasted cardio can negatively impact performance, especially during high-intensity workouts (HIIT). The lack of readily available carbohydrates can lead to fatigue and decreased endurance, hindering your ability to push yourself during intense exercise.

If protein intake isn't prioritized, fasted cardio can lead to muscle breakdown, as the body seeks alternative fuel sources. Without sufficient nutrients, the body may turn to muscle tissue for energy, potentially undermining the goal of preserving lean muscle mass during a fat-loss journey.

Not everyone experiences fasted cardio well. Some individuals may experience increased feelings of hunger and low energy levels, making it challenging to sustain workouts and potentially leading to overeating later in the day.


Should You Try Fasted Cardio?​

It's essential to remember that fasted cardio is optional for achieving fat loss. Numerous other factors, including diet, overall calorie intake, and exercise consistency, play a significantly more significant role in weight management. Some individuals may perform better and experience more significant overall benefits from consuming a pre-workout meal that provides readily available energy for their workouts.

While fasted cardio may not be universally necessary, specific individuals may find it well-suited to their preferences and lifestyles. Those who enjoy morning workouts, have a good base fitness level, and prioritize post-workout nutrition may be ideal candidates for incorporating fasted cardio into their routine.

Safety should always be a top priority whether you engage in fasted cardio or opt for a pre-workout meal. Listening to your body is paramount. If you experience dizziness, weakness, or excessive fatigue during exercise, it may be a sign that your body needs fuel before the workout.

Consulting a healthcare professional or registered dietitian is highly recommended before embarking on fasted cardio, especially if you have any underlying health conditions, such as diabetes or low blood sugar. They can help determine if this approach aligns with your health and fitness goals and guide safe implementation.

Fasted Cardio Tips​

Start Slow and Steady​

When venturing into fasted cardio, it's essential to begin gradually. Opt for shorter, low-intensity workouts (LISS) like walking, swimming, or light jogging. It allows your body to adapt to exercising in a fasted state and prevents potential adverse effects like dizziness or fatigue. As you adjust, you can gradually increase the duration and intensity of your workouts.

Fueling Your Body: Focus on Nutrition​

After your session, prioritize meals rich in protein and essential nutrients for recovery and muscle preservation.

Protein intake is particularly crucial, as it aids in muscle repair and helps mitigate the potential for muscle breakdown during fasted exercise. Consider incorporating protein-rich sources such as eggs, yogurt, lean meats, or plant-based alternatives into your post-workout meals.

Staying hydrated is equally crucial, especially when exercising on an empty stomach. Adequate fluid intake, including electrolytes, helps maintain hydration levels and supports overall performance. Dehydration can exacerbate feelings of fatigue and discomfort, making it essential to prioritize fluid intake throughout the exercise session.


The ideal fasting window for fasted cardio varies depending on metabolism and sleep patterns. Some individuals might succeed with exercising after an overnight fast, while others might benefit from an intermittent, like skipping breakfast and exercising mid-morning.

Finding the optimal timing for fasted cardio can enhance its effectiveness and fit seamlessly into your daily life. Experiment and observe how your body responds to different timings to identify what works best.

Sustainability is Paramount​

Remember, fasted cardio is not a magic bullet for fat loss. Sustainable fitness practices contribute to long-term success and overall well-being. Instead of rushing into an intense fasted cardio regimen, prioritize a gradual and sustainable approach.

Combine fasted cardio workouts with healthy lifestyle choices like a balanced diet, regular exercise, and adequate sleep.

Frequently Asked Questions​

Can I do any type of exercise while fasting?

  • High-intensity workouts may be challenging without sufficient fuel, while you can perform light to moderate exercises like walking or yoga while fasting. Listen to your body and consider low-impact activities during fasted states to avoid potential fatigue or dizziness.

Does Fasted Cardio burn more fat than regular cardio?

Fasted cardio may increase fat burning during the workout, but overall fat loss depends on diet and consistency.

Is Fasted Cardio good for building endurance?

Fasted cardio can improve endurance over time, especially if done regularly. Training in a fasted state encourages the body to use fat for fuel, potentially enhancing endurance. However, a balanced approach to training is essential for optimal results.

How often should I do fasted cardio?

A common approach is starting with 1-3 weekly sessions and gradually increasing intensity and duration. It's crucial to balance fasted and fed workouts for overall fitness.

How long should I fast before my workout?

The ideal duration for fasting before a workout varies among individuals. Many engage in overnight fasts of 8-12 hours before morning workouts.

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