My Thoughts On Intermittent Fasting

Intermittent fasting has gained significant popularity in recent years, not only among those looking to lose weight but also among athletes seeking to optimize their performance. This eating pattern involves cycling between periods of fasting and eating, and it has been shown to offer numerous benefits for both physical and mental well-being. I'll be sharing my experiences integrating intermittent fasting into my training regimen, and how it has allowed me to stay relatively fit all-year round.

My Journey to Intermittent Fasting

I started intermittent fasting in 2020. I had completed a demanding season of training and racing in 2019 and needed a break from running and cycling. I had been training upwards of twenty hours a week in the lead up to Ironman Korea and without any specific races in mind in the coming year, I started to slack off when it came to cardiovascular training.

During my peak training blocks, my active caloric burn topped out at around two thousand five hundred calories and my inactive burn was roughly about one thousand calories a day, so I could pretty much eat whatever I wanted without gaining weight. If anything, I couldn't consume enough to satisfy my insatiable hunger. However, once I significantly decreased my training, the hunger persisted which led to fluctuations in both energy and weight.  

I first heard of intermittent fasting through a friend and did a bit of research on the benefits (more below).  The main reasons why I wanted to give intermittent fasting a try were 1) maintain a moderate weight/keep off body fat 2) reduce the afternoon energy lull 3) increase my cognitive clarity and focus.  My main concerns were 1) whether fasting was sustainable given that I always felt hungry 2) potential loss of muscle and physical strength 3) mood swings due to lack of energy/being hungry. 

I slowly transitioned my eating habits to fit into a 16/8: Intermittent Fasting Plan, in which the time restricted eating window was between 12:00pm and 8:00pm.   I had typically eaten breakfast at around 8:00am after my first training session and finished my last meal by 7:00pm.  Over four weeks, I ate smaller meals for breakfast and an hour later each week to progressively eliminate the need to have a full meal at breakfast.   In the beginning it was a struggle, because I was so accustomed to feeling full throughout the morning.  Whenever I felt hungry, I drank water instead.  By the time I had fully adjusted to the 16/8 Plan, I felt more energetic in the morning and didn't feel a significant dip in energy after I ate.  There was also a noticeable shift in my clarity of mind; I no longer felt groggy and the lethargic after waking up.  

By restricting the amount of carbohydrates I ate in the evening during my feeding window, my body maintained limited glycogen (readily available energy source for the body) stores overnight.  My body adapted to utilizing the limited stores of glycogen and fat as fuel, while completing my workouts and cold plunges first thing in the morning. Despite reducing my training significantly,  I have maintained the same weight while putting on more muscle by intermittent fasting.

Benefits of intermittent fasting

1. Enhanced Fat Burning: Intermittent fasting taps into their body's fat stores more efficiently. During the fasting period, when glycogen levels are depleted, the body turns to fat as its primary source of energy. This can lead to a reduction in body fat percentage and improved body composition.  

2. Increased Insulin Sensitivity: Intermittent fasting has been shown to improve insulin sensitivity. Improved insulin sensitivity means that the body can utilize carbohydrates more effectively, leading to better energy utilization.

3. Boosted Growth Hormone Levels: Intermittent fasting has been linked to increased production of growth hormone, which plays a vital role in muscle growth, repair, and recovery. Higher growth hormone levels can help build lean muscle mass.

4. Enhanced Cellular Repair: During fasting periods, the body initiates a cellular repair process called autophagy. This process helps remove damaged cells and proteins, promoting cellular rejuvenation and overall health. Improved cellular repair can aid in muscle recovery and reduce the risk of injury.

5. Mental Clarity and Focus: Intermittent fasting has been reported to enhance mental clarity and focus. By promoting the production of ketones, the brain's preferred source of energy during fasting, you can experience increased cognitive function and improved concentration during.

Tips for intermittent fasting 

1. Start Slow: Begin by gradually increasing the fasting window. Start with a 12-hour fast overnight and gradually extend it to 14 or 16 hours. Listen to your body and adjust accordingly.  Talk to your doctor to see if intermittent fasting would be recommended based on your current circumstances.  

2. Stay Hydrated: Hydration is crucial during fasting periods. Make sure to drink plenty of water and electrolytes to stay properly hydrated and support optimal bodily functions.  By drinking a water, you will temporarily feel satiated.  

4. Focus on Nutrient-Dense Foods: When breaking the fast, prioritize nutrient-dense foods to provide your body with the necessary fuel and nutrients. Include lean proteins, healthy fats, and complex carbohydrate.  When I am strength training, I typically focus on consuming higher proportions of lean proteins (chicken, fish, turkey, etc) and less carbohydrates (i.e. rice, pasta, potatoes); however, when I 

5. Listen to Your Body: Everyone is different, and what works for one may not work for another. Pay attention to how your body responds to intermittent fasting and adjust accordingly. If you experience any negative effects or notice a decline in performance, consult with a healthcare professional or sports nutritionist.

Age 35, 145lbs, 11% BF - Jan 2024

Goals: Ironman and Marathon Training and Intermittent Fasting 

For 2024, my athletic goals are very ambitious.  I am currently training to break all of my previous personal best times for the 10km, half-marathon, marathon and Ironman distances.  I've ramped my endurance training (primarily running and biking) to prepare for the rigorous demands of ten to eleven race-pace efforts.  Given the caloric demands of the training that I am doing, I am currently cycling off my intermittent fasting plan so I have sufficient protein, carbohydrates and fats before and after each training session.  To prepare for my races, I need to train under race-like conditions. To ensure my body is accustomed to digesting and absorbing the foods that I eat, I am not able to maintain the eight hour feeding window.  Once I return to strictly strength training, I will likely return to intermittent fasting.  

Caloric Balance 

At the end of the day, intermittent fasting is simply a way to balance the calories you consume with the calories you expend.  If my goal was to lose weight by intermittent fasting, but I consumed the same number of calories I did with three meals, all else being the same, I wouldn't lose any weight. Putting this into context, to lose one pound of fat, you would need to be at a caloric deficit of three thousand five hundred calories.  A typical American breakfast might include options like eggs, bacon or sausage, toast or bagels, cereal, fruit, and coffee or juice which could range from 300 to 600 calories or more.  By eliminating breakfast for a week, one could (in-theory) lose one pound of fat per week and not have to exercise any more than they currently do.  Whereas, if you wanted to burn off six hundred calories by walking, you would need to walk six miles/~ten kilometers (assuming you can burn one hundred calories per mile.  

I wouldn't call intermittent fasting a diet, because the purpose of the time restricted window for consuming your meals is to reduce the overall calories being consumed.  What makes this protocol so effective in my opinion is that you are still intaking (hopefully) a well balanced diet consisting of the necessary fats, carbohydrates, and proteins, as opposed to the Atkins, Carnivore, Vegan Diets which all over index on one more macro.  

Take Aways 

After intermittent fasting for over three years now, I have developed a good grasp of what my body needs in terms of caloric input/output to maintain a healthy body composition.  I look at intermittent fasting as a tool in my toolbox which can be utilized at different points in my life as needed.  I am constantly challenging my body, so depending on the the demands of those activities, I will integrate different protocols (i.e. fasting) to optimize my nutritional needs.  I can't say that intermittent fasting is for everyone, but I do believe that there are compelling reasons to at least give it a try.  If you want to learn more about intermittent fasting, I'd recommend listening to Andrew Huberman's podcast - Effects of Fasting & Time Restricted Eating on Fat Loss.