Intermittent Fasting and Working Out: A Comprehensive Guide
A common concern among those practicing intermittent fasting is the potential loss of muscle mass, particularly if they are exercising during the fasting window. This article aims to dispel these concerns and explain the benefits of training while fasting versus training after eating. We will also delve into the physiological processes that occur in each scenario, enabling you to make an informed decision about whether to work out on an empty stomach.
Why You Don't Lose Muscle Mass When Working Out While Fasting
Many wonder why they don't consume muscle mass when exercising during a fast, despite having low resources in the body. Scientific evidence indicates an increase in testosterone and growth hormone during fasting. These anabolic hormones develop muscle mass, compensating for the catabolism process (tissue degradation) that occurs during fasting.
Interestingly, after fasting for several hours, your body begins to produce ketone bodies. These products prevent the oxidation and breakdown of an amino acid called leucine, which is essential for muscle mass preservation.
The Physiology of Working Out While Fasting
Research published in the Journal of Physiology on fasted training reveals that during fasting workouts, you consume your glycogen reserves (sugars in your muscle mass) and start to use intermyofibrillar lipid reserves. These lipid reserves, found within muscle fibers, are microscopic drops of fatty acids used as an energy source once glycogen reserves are depleted.
This process only occurs when working out while fasting. It essentially involves the loss of fat from within your muscles, transforming it into energy once your glycogen and sugar reserves are depleted.
The Benefits of Burning Fat Inside Your Muscles
You might wonder why you would want to burn fat inside your muscles rather than from areas like your abdomen. The key is understanding that once this intramuscular fat is consumed, it must be replenished. Your body mobilizes fat from other reserves to your muscles to renew it when you're recovering the muscle fibers you exercised. However, this process only occurs if you train while fasting.
Optimal Fasting Duration for Exercise
The studies mentioned found benefits in patients who trained after only 12 hours of fasting. This is achievable for most people and can lead to a significant reduction in fat inside your muscles.
High-Performance Athletes and Fasting
High-performance athletes often worry about their performance in competition if they don't consume carbohydrates normally. If you usually train while fasting but don't want to be fasting during competition, you can do a process called carbohydrate cycling. This involves eating a very low carbohydrate diet when training, but replenishing your muscle glycogen stores before the competition.
This is beneficial because studies show that people who usually train while fasted replenish their muscle glycogen stores three times faster than those who don't.
The Role of Insulin Sensitivity
This rapid recovery is due to increased insulin sensitivity. Insulin is a hormone that manages your blood sugar levels. If you train fasted, you increase your sensitivity to insulin, facilitating faster recovery of glycogen stores.
Conclusion
If you work out after fasting for 12 hours, you increase your fat intake to transform it into energy, helping you burn more fat. If you work out after 15 or 16 hours of fasting, you increase the sectors of your body dedicated to transforming fat into energy.
To optimize fat loss, consider a combination of three things:
- Lowering the glycemic index of your diet to keep blood sugar low and stable, avoiding high insulin values.
- Practicing intermittent fasting.
- Engaging in HIIT training to accelerate your metabolic speed.
For more information, consult with one of our Fitness Experts on our Mavyn website. Our Nutrition Mavyn Experts will also be available soon to answer any nutritional questions you may have.