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Fasting Considerations for Cognitive and Athletic Performance

by | Sep 13, 2021 | MOVING/RESTING

Do you ever feel foggy in the brain, unable to think quickly on your feet?  Do you stumble through your workouts, unable to power through and move quickly on your feet?  There is a connection between your mind and body.  Thinking quickly on your feet and moving quickly on your feet both require flipping that fasting switch.  Learn how fasting improves your brain function and gets your body running in prime athletic performance. 

Fasting Benefits Quickness in Cognitive and Athletic Performance 


How to flip that fasting switch

Fasting is a purposeful dietary method with partial or complete abstinence from eating for periods of time.  This causes your body to go through a process called intermittent metabolic switching.  Depending on your fasting method, the overall goal is to turn on that fasting switch. 

Intermittent metabolic switching involves fasting periods where your body completely depletes its liver glycogen (sugar) stores.  The depletion of glycogen stores converts your body’s fat stores into ketone bodies for energy turning on that G to K switch (glycogen to ketone switch). 

There are different intermittent fasting regimens activating that G to K switch.  Some fasting methods require limiting certain foods, beverages, or all foods during fasting timeframes.  It could be for a certain number of hours, days, or interchanging days, or many days during the week of fasting. Food is consumed during the set ‘feeding’ times.  Water intake is not usually restricted.  Here are some of the most common types of intermittent fasting:

  • Time-restricted: This involves not eating for a set number of hours, including the time asleep.  Food is consumed food during the remainder of the 24-hour period.  For example, the 12:12 model involves fasting for 12 hours, followed by eating all foods within your normal caloric intake for the remainder 12 hours.  The 16:8 model is the one most commonly used with 16 hours of fasting and 8 hours of eating. 
  • Alternate day fasting involves fasting and feeding on alternate days during certain days of the week. Caloric intake is limited to 500 calories on fasting days. On feeding days, food consumption is not limited.  For example, in the 5:2 model, caloric intake is limited to 500 calories per day for two days in a row.  During the other five days of the week, there are no restrictions on food consumption. 

Getting your brain up to speed

Thinking quickly on your feet requires turning on that intermittent metabolic switch.  Turning on that G to K switch during fasting causes a series of cell signaling reactions promoting brain health. 

Neuroplasticity or remodeling in the brain is promoted through intermittent fasting.  Both IGF-1 (insulin growth factor 1) and BDNF (brain-derived neurotrophic factor) increase forming new brain cells causing thickening of the gray matter in your brain, called the hippocampus.  

In particular, the CA1 layers of the hippocampus are increased.  Like an Intel computer processing chip, this is the area of the brain responsible for your memory processing speed.  Learning, forming, synthesizing, and retrieving short-term memory occurs in this area of the hippocampus.  This area of the brain is also responsible for turning your short-term memory into long-term memories. 

Oxidative stress, a marker for aging in the brain is reduced.  Hence markers of oxidative stress such as brain fog, brain fatigue, headaches, and memory loss often diminish.  Autophagy or purging of damaged brain cells promotes the formation of healthier brain cells.  These healthier brain cells function more efficiently helping you react and respond quickly to new information. With practice, it becomes a ‘two-for-one deal’ because motor control improves, allowing you both to think quickly on your feet AND move quickly on your feet. 

Body composition for athletic performance

Regardless of the sport or physical activity, athletic performance requires optimal power, speed, agility, and strength with larger amounts of lean mass (muscle and bone) and a lower amount of body fat.  For this reason, athletes commonly need to reduce weight for sports purposes.  Competition-winning sprinters and endurance athletes typically have lower amounts of body fat. 

Turning on that G to K switch reduces your body weight and the fat stores found in your body.  Hence improving your body composition.  Whether you’re an athlete or a highly or moderately physically active individual, the overall goal is to reduce fat mass, while retaining lean muscle in order not to jeopardize training and performance. 

Fasting and nutrient density

Training and performance may not be jeopardized with these essential nutritional factors during feeding/fasting: 

  • Total daily macronutrient and micronutrient composition based on the energy demands of sport or physical activity.
  • Specific timing and distribution of nutrient consumption throughout feeding times.
  • Necessary supplements may be the game-changers based on the person’s needs.

Paying attention to daily caloric and micronutrient requirements is vital during heavy training sessions.  For this reason, nutritional components substantially impact body composition for athletic performance.  Hence, the focus of fasting for athletic performance is eating whole foods like vegetables, whole grains, and high-fiber foods during feeding times.  Of course, avoiding and limiting junk food and high sugar content foods is also part of the objective of optimizing your fasting regimen for achieving a healthy body composition. 

Nutrient density not only plays a crucial role in augmenting an athlete’s training, performance, and recovery.  It is also vital for immune, endocrine, and musculoskeletal function.  For physically active women, paying attention to micronutrient density and healthy body composition is vital for proper endocrine and reproductive function.  Low iron status is often found in physically active women. 

Since another type of fasting method, caloric restriction, involves reducing 20-40% of your daily caloric intake, it is usually not recommended for athletes or highly physically active individuals.  The energy demands of the type of physical activity and sport are crucial for peak athletic performance. 

Adaptation for athletic performance

Humans are biological creatures.  Environmental adaptation is inevitable.  Charles Darwin once said, “It is not the strongest or the most intelligent to survive, it is the most adaptable to change”.  Your environment includes your diet.  Adaptation by your body is a key factor for the proper implementation of fasting methods. 

Intermittent fasting methods, particularly time-restricted feeding is considered one of the most adaptable fasting methods for athletic performance.  Hence, your fasting method must be used for several days. 

The key is knowing when and how to exercise and compete. 

Fasting considerations for athletic performance

Although body composition through fasting methods may improve, these considerations must be taken for optimizing athletic performance: 

  • Training level: Studies have shown elite athletes adapt quickly to their fuel sources, called metabolic flexibility.  Due to training and experience, the athletic ability may take over regardless of fuel source.  Alternately, untrained individuals may require longer adaptation periods to fasting methods. 
  • Adaptation period for fasting: Long-term versus short-term adaptation may allow the body to adjust to calorie deficits during exercise sessions. 
  • Exercise type: Aerobic exercise or anaerobic exercise may determine the primary fuel source for the exercise.  Aerobic exercise is continuous exercise generally lasting greater than 30 minutes.  Conversely, anaerobic exercise involves intermittent exercise bouts with rest periods.   Feeding and fasting intervals may affect the type of exercise.   
  • Exercise intensity: The amount of energy deficit during the fasted state may affect the ability to exercise intensely.  Poor athletic performance in high-intensity anaerobic exercise has been reported in studies with less than 4 days of adaptation to fasting methods.    
  • Meal composition: Macronutrient and micronutrient composition during feeding times may affect performance levels depending on the type of exercise. 
  • Glycemic Index: Blood sugar levels do not increase as greatly with low to moderate glycemic index foods.  On the contrary, high glycemic index foods spike blood sugar levels.  The glycemic index of foods during feeding times may affect athletic performance depending on the type of exercise.
  • Training season: Since athletes during in-season and competition have special nutritional energy and metabolic demands, off-season and pre-season may be more suitable times for fasting adaptation. 
  • Hydration status: Dehydration may affect your ability to exercise intensely, or exercise for long periods of time. 
  • Age: Children and teenagers have increased calorie and nutrition needs due to growth and development.  Fasting is not recommended for athletic performance. 
  • Pregnancy or breastfeeding: Women who are pregnant or breastfeeding have specific nutritional needs where fasting is not recommended for athletic performance.
  • Medical conditions: Fasting is not recommended for persons with medical conditions such as diabetes, cardiovascular disease, or taking blood pressure medications.  

Flipping that fasting switch may get your brain and body running at optimal performance.  With practice, it may become that ‘game-changing’ ‘two-for-one deal’ allowing both thinking and reacting quickly on your feet.