Training On An Empty Stomach

Apr 30, 2024 | by Jennifer Dabbak

Training on an empty stomach has been a popular topic in the fitness world, especially with the increasing number of people on an intermittent fasting diet,  with so many advocating its potential benefits for fat loss and metabolic health. But is exercising without having eaten anything beforehand truly advantageous, or could it do more harm than good? Let’s delve into the subject, exploring the science behind fasted workouts and weighing the pros and cons in simple yet logical terms.

Understanding Fasted Workouts:

When we talk about training on an empty stomach, we’re referring to exercising without consuming food in the hours leading up to the workout. The idea behind this approach is that by exercising in a fasted state, the body may rely more on stored fat for energy rather than the carbohydrates we consume in our meals.

Pros of Training on an Empty Stomach:

1-Fat Burning Potential: Exercising in a fasted state could potentially enhance fat burning. Without recently consumed carbohydrates to fuel activity, the body may turn to fat stores for energy, aiding in fat loss over time. When you engage in physical activity without having consumed food beforehand, your body’s glycogen stores, which are the primary source of energy, become depleted. In the absence of readily available glycogen, your body shifts its fuel source to stored fat, leading to increased fat oxidation during the workout. This process is thought to occur because insulin levels are typically lower during fasting, allowing for greater mobilisation and utilisation of fat stores for energy.

2-Improved Insulin Sensitivity: Fasted workouts have been shown to improve insulin sensitivity, which is essential for regulating blood sugar levels. When you exercise on an empty stomach, particularly in the morning before eating, insulin levels are typically lower, allowing your body to better utilise glucose and regulate blood sugar levels more efficiently. Enhanced insulin sensitivity can reduce the risk of insulin resistance and type 2 diabetes, promoting overall metabolic health. 

3-Growth Hormone Release: Fasted training, particularly in the morning before consuming food, has been associated with an increase in human growth hormone (HGH) levels. HGH is a hormone produced by the pituitary gland that plays a crucial role in growth, metabolism, and muscle development. During fasted exercise, the body’s glycogen stores become depleted, prompting it to rely more on fat for energy. As a result, insulin levels decrease, while counter-regulatory hormones like glucagon and adrenaline increase, signalling the body to release stored energy sources. This, combined with the stress of exercise, can stimulate the secretion of HGH. Elevated HGH levels may promote fat metabolism, preserve lean muscle mass, and support tissue repair and growth.

Cons of Training on an Empty Stomach:

1-Decreased Performance: Exercising without fuel in your system may lead to decreased performance and reduced intensity during workouts. Without sufficient energy from food, you may feel fatigued more quickly, limiting your ability to push yourself. Exercising on an empty stomach means that the body has limited glycogen stores available for energy, which can result in reduced stamina, strength, and endurance during the workout. Without adequate fuel, the body may struggle to maintain intensity and may fatigue more quickly. Additionally, low blood sugar levels during fasted training can impair cognitive function, focus, and coordination, further impacting performance. The extent of performance decrements can vary depending on factors such as the duration and intensity of the exercise, individual metabolism, and overall fitness level.

2-Muscle Loss Risk: While fasted workouts can promote fat burning, there’s also a risk of muscle breakdown. This is caused by a higher secretion of Cortisol which is a stress hormone. Without proper fuel, the body may resort to breaking down muscle tissue for energy, potentially compromising muscle growth efforts. After a fasted workout, there’s potential for muscle loss, particularly if the body is in a prolonged catabolic state where it’s breaking down muscle tissue for energy. With limited glycogen stores available for energy during fasted training, the body may turn to muscle protein as a fuel source, especially in the absence of adequate amino acids from food intake. While moderate fasted workouts may not significantly impact muscle mass in well-nourished individuals, extended periods of fasting combined with intense exercise could potentially lead to muscle catabolism

3-Increased Injury Risk: Training on an empty stomach could increase the risk of muscle injury. Without adequate glycogen stores for energy, muscles may fatigue more easily, increasing the likelihood of strains, sprains, or other injuries, particularly during high-intensity activities. Additionally, low blood sugar levels during fasted workouts can impair cognitive function and coordination, reducing focus and reaction time, further elevating the risk of accidents or overexertion. Dehydration, which can occur more readily during fasted exercise if adequate fluids are not consumed, can also impair muscle function and increase susceptibility to injury. To mitigate the risk of injury during fasted training, it’s essential to prioritise proper warm-up exercises and maintain good hydration.

Finding Balance and Listening to Your Body:

Finding balance and listening to your body are essential in any fitness regimen, including fasted training. While fasted workouts may offer many benefits, it’s crucial to recognize individual differences and responses. Paying attention to your body’s cues, such as energy levels, hunger signals, and overall well-being, can help guide your exercise decisions and ensure that you’re training safely and effectively. Achieving a balance between pushing your limits and respecting your body’s limits is key to preventing overtraining and injury. If you’re feeling excessively fatigued, lightheaded, or experiencing discomfort during fasted training, it’s essential to listen to these warning signs and adjust your approach accordingly. Incorporating rest days, nourishing your body with proper nutrition, and staying hydrated are essential components of maintaining balance and supporting overall health and fitness goals. By having a mindful and intuitive approach to exercise, you can optimise your performance, minimise the risk of injury, and embrace a sustainable and enjoyable fitness journey.

Tips for Safe and Effective Fasted Workouts:

1-Stay Hydrated: Drink plenty of water before, during, and after your workout to stay hydrated, especially when exercising in a fasted state.

2-Start Slowly: If you’re new to fasted workouts, start with shorter, less intense sessions to gauge how your body responds. Gradually increase the duration and intensity as you become more accustomed to training on an empty stomach.

3-Refuel Afterwards: After completing your workout, be sure to refuel your body with a balanced meal, a protein shake(ideally whey), or a snack containing carbohydrates and protein to support recovery and muscle repair.

In Conclusion:

Training on an empty stomach can have both potential benefits and drawbacks, and the key is finding what works best for you. While some individuals may experience increased fat burning and improved metabolic health from fasted workouts, others may find that it negatively impacts their performance and recovery. As with any aspect of fitness and nutrition, it’s essential to listen to your body, experiment with different approaches, and find a balance that supports your goals and overall well-being.


Jennifer Dabbak

Jennifer Dabbak

Jennifer has been a Fitness coach at AIF for almost 10 years. She completed a Bachelor Degree in Physical Education and Sports in Lebanon where she started working as a Personal Trainer. Figure skating is what started her passion for fitness and exercise. She has been working in the industry for over a decade and she completed numerous courses in rehab, massage, boxing and Strength and Conditioning. Jennifer also runs her own small business from her garage, where she trains one on one clients.

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