Metabolic Flexibility & Fasting
There is a truly insane amount of different approaches that have been created regarding diet & nutritional advice. Not only is much of this information overly generalized and not helpful, much if it is flat out incorrect. We live in a world rich in information but poor in knowledge. Through years of self-experimentation and an obsession with fitness podcasts I’ve synthesized some of my own guiding principles. Below are the keys to optimal nutrition (in my opinion):
I. Metabolic Flexibility
The most important thing that I’ve learned can be summarize by two words, Metabolic Flexibility. My goal in life is not to be keto forever, restrict foods so much that I can’t enjoy family dinners, or spend time obsessing over food. The goal is to train your body to be adaptive, flexible, and sensitive.
The truth can be frustrating, there is no correct nutritional advice that you can tell a large group of people. Our bodies are too unique, too different, and so are our lifestyles. In my eyes the goal should not be to craft one nifty plan and sell it to the masses. Everyone has heard of the saying “you give a man a fish and he eats for a day, teach him how to fish and he’ll eat for a lifetime.” Well it’s time to go fishing. My goal is to help you get connected with your body and become more aware. I want you to have the skills and knowledge to realize the affect different variables have on your body. This way you are not bound to your routines every day of your waking life. After all, routines are boring. True signs of a powerful diet is being on a family vacation/business trip in a strange country and using your understanding of food to stay on track with your goals, without being so restrictive that you ruin the experience for others involved. Remember we are after the greatest benefit with the least amount of effort and disruption. Now enough laying of the landscape. Let’s get into some principles.
Our bodies have two main energy pathways, glycolysis and lipolysis. Glycolysis, as the name infers, means that you are burning glycogen from carbohydrates as energy while lipolysis describes the process of using fat (consumed & stored for energy). Neither is considered good or bad, there’s a use case for both energy pathways. For example athletes that work at very high heart-rate levels doing vigorous muscular and cardiovascular training simply need carbs to fuel these activities. If you’ve ever read about Michael Phelps’ diet full of french toast and pancakes, then this shouldn’t be a surprise. Metabolic Flexibility refers to the ability to switch between burning fat or burning carbs easily, as during different times of your life you will need different fuel sources.
My personal diet varies incredibly. Every Monday I do a 24 hour fast and save exercise for the end of the day, so that I can give my body a digestive break and be time efficient with work (Mondays are typically very busy). In contrast I like to go surfing on weekend mornings, and then do a 1–1.5 hour lift later in the day. On Monday I will often eat no carbs, or very little (<80g) after my evening workout. This is because my body simply doesn’t need them. Then on the weekend days I will eat nearly every carb in sight, since I have the time to be active. These are the days where I indulge in pasta, burritos, sushi, really whatever I feel like. My body’s depleted and will therefore be receptive the glycogen as a fuel source & to rebuild muscle— NOT something that will be stored as fat. In addition having the weekends to give myself a little break and not have to worry about what restaurant my friends want to go to is a very nice thing. It has made being stricter during the week very easy for me.
Key Takeaway: Think of your body from an objective perspective. When you’re super active, have some healthy carbs (Phelps can have sugary IHOP pancakes, but that doesn’t mean you should). When you’re busy with work, kids, school, whatever…stick to mainly fats and proteins. Strengthening each of the energy pathways, and limiting blood sugar spikes throughout the day by only having carbs around exercising will serve you very well. Both from an aesthetic point of view and from a long-term health perspective.
II. Intermittent Fasting
Fasting has re-entered the zeitgeist in recent years, but is a practice as ancient as humanity itself. Consider the fact that there are hundreds of religions, who disagree on nearly everything, but all have a history of fasting built into their practices. This itself heightens my interest immensely.
The act of fasting can be borderline cult-like, as most things in the fitness world. This makes it intimidating to start as a newbie, and throws a veil of mystery over what fasting actually is. My personal journey was plagued by such prophetic characteristics which made landing upon my ideal routine drag out a few years. Therefore I will never try to tell you what to do, but rather present my understanding of potential levers / customizations. Hopefully this rundown will expedite your personal journey.
How long?
Some purists consider the word “fasting” to mean at least 24 hours without calories. There’s also the group that believes dry fasting, meaning a fast without drinking any liquids or even allowing skin contact to water, is the best method. I personally don’t want to do 5+ day fasts, or spend all day thirsty and smelly. Fasting is a tool for me to perform better in other aspects of life; so you could say that I fast to live, not live to fast. Before you play around with lengthy fasts (18+ hours) I highly recommend letting your body ease into it.
Start with 12 hours and make sure your last meal is low-carb, so that you activate the using of fat as energy rather than glucose. If you have a high carb meal and then try to fast you will be inherently more hungry and even break down protein/muscle into glucose (through a process known as gluconeogenesis). After getting comfortable hear I’d recommend going for the 16–18 hour fasts. For someone with an active lifestyle I have personally found these the best! You can get low energy and poor recovery if pairing extended fasts along with intense training, especially for someone who doesn’t have a ton of bodyfat. Aside from that I do 1 refeed every Sunday (paired with leg training) and a 24-hour fast Monday to get some autophagy and free up more time for work. Here’s an easy diagram to break up my rambling :)
It’s also important to note that when you fast your endogenous digestive enzyme production slows down significantly. Therefore it’s not smart to break your fast with a big meal, and safer to stick to ~500 calories worth of proteins and fats. After this first meal, your stomach will be warmed up and you’re free to eat whatever. Enjoy the process of getting to know your body! Everyone’s different so find out what works for you, and don’t force the same fast 24/7/365. Switching up your routine will be a nice mental break and hermetic stress that’ll even make your body stronger.
Disclaimer: due to biological differences, mainly regarding hormones, women should be more careful when fasting for long periods of time. Fasts for >24 hours are more often negative for women.
What does fasting do?
- You become more insulin sensitive as meal frequencies go down and your blood sugar is more stable throughout the day
- Deplete your glycogen stores and thereby start mobilizing visceral fat (the really bad fat that sits around your organs)
- Ketone production raises after the 12 hour mark, which is shown to have great cognitive & neuroprotective effects (lowering risks of disorders such as dementia, Alzheimer's, etc.)
- Support weight loss as you become more conscious of your diet
- Boost growth hormone and stem cell production (for longer fasts in the 18–36 hour range)
- May improve heart health by improving blood pressure, triglycerides and cholesterol levels
- Promotes longevity due to various aspects such as decreased inflammation, blood sugar control, healthy microbiome, and more which are still being studied
- Helps clear the skin and prevent acne
Where did you go wrong?
See some of the mistakes I made on my journey, which you should definitely be aware of before starting your experiment.
- Don’t burn the candle at both ends. Days in which you fast for 24 hours are not conducive to heavy weight training. Your nervous system will be shot and recovery near impossible.
- Ease into it. Your body is delicate and you won’t get the results wanted with sheer will power.
- Get the macronutrient ratios right. Life is much harder than it needs to be if you go from a high carb feast straight into fasting. The cravings are brutal.
- Know the signs of a fast that’s going on too long. Mine are typically coldness (especially on hands & feet), a headache, cramping, and occasional dizziness from low blood sugar.
- Don’t overdo the caffeine intake. Coffee and tea are awesome for driving up your metabolism & mobilizing fatty acids, but they also make your body excrete a lot of minerals. Such dehydration can be very detrimental so take it easy on the caffeine and try adding in some magnesium supplements.
- Breaking your fast with a big meal is a recipe for disaster. It’ll make you feel bloated, cause severe stomach pain / digestive issues, and counteract all of the good feelings you’ve experienced.
Getting to know your body is, in my opinion, one of the most overlooked but necessary aspects of life. This body is kind of all that you truly “own” so enjoy it and embark on the lifelong journey of becoming your best self. Such pursuits are a luxury, which I’m grateful to be able to do.
