How to boost your mental energy with intermittent fasting

As the runner-up to light, nutrition is the second most powerful time giver controlling our circadian rhythm.

The timing, quality and quantity of what we ingest also help us maintain relatively high levels of mental energy during the day and lower our autonomic arousal in the evening, which goes a long way toward minimizing stress.

Chances are you’re familiar with what the reverse feels like. The roller coaster ride in mental energy (and blood glucose) after a sugary breakfast in the morning, the food coma in the afternoon, or the trouble with sleep after a too-big (or too-small) dinner.

All of these feel stressful. If we want to be productive in the morning but have a low or unstable level of mental energy, this creates stress. If we want to fall asleep in the evening when our minds or bodies are still working at full speed, we’ll have problems winding down, which also feels stressful.

Last week, I explained how to strategically use caffeine and water to minimize that kind of stress by optimizing your mental energy throughout the day. Today’s post is the first of two on how to pull off the same trick with food.

What (not) eating around the clock does to your body

Regarding nutrition, there’s one notion that most of us have learned in our childhood: Eating three meals a day and having snacks in between is good for us. Doing so, we have been told, constantly provides us with the (caloric) energy that we need to remain healthy throughout our life and productive throughout our day.

Yet, there's a problem with that notion: The research actually points to the opposite.

Whenever we eat, the cells in our liver and muscles create and store fat. When we eat around the clock, our body is stuck in this “fat-creation mode”. At the same time, “glucose created from digested carbohydrates floods our blood and the liver becomes inefficient in its ability to absorb glucose”, writes Satchin Panda in The Circadian Code. He concludes that “if this continues for a few days, blood glucose continues to rise and reaches the danger zone of prediabetes or diabetes”.

A better alternative, which has become increasingly popular over the last decade, is intermittent fasting (IF). Its most popular form includes having episodes of not ingesting anything that contains calories for about 16 hours each day (give or take 2 hours).

As Mark Mattson describes in his book on the topic, IF comes with many benefits. In our body, it leads to weight loss and protects against diabetes, cardiovascular disease, and cancer. In our brain, it improves learning and memory, reduces levels of anxiety, and protects against neurological disorders, including Alzheimer’s disease and stroke.

On top of that, IF is also great for optimizing our mental energy and productivity day in and day out.

Why fasting improves your productivity

The Greek philosopher Plato once said: “I fast for greater physical and mental efficiency”.

More than two millennia later – yet still over a century before scientists first revealed its health benefits in humans – former surgeon Edward Dewey published The No-Breakfast Plan and the Fasting Cure in 1900. In this book, he pioneers recommending 16- to 18-hour fasts every day by skipping breakfast and eating only two meals per day, according to Mattson.

Apart from its (then still assumed) health benefits, Dewey praised the productivity boost he got from working in a fasted state, writing that “there were forenoons of the highest physical energy, the clearest condition of mind, and the acutest sense of everything enjoyable”.

In the Circadian Code, Panda explains why: “The brain actually works better on an empty stomach. We are not very alert after we finish a meal”. […] This may relate to our inherent survival strategy. When we are hungry, our brain must find creative ways to search for food”.

If you think about how our Paleolithic ancestors used to live many millennia before Dewey (and Plato), this makes intuitive sense: Hunter-gatherers wouldn’t have survived unless their brains were functioning at a high level when there was no food. The most advanced capabilities of the human brain – including logical thinking, language, imagination and creativity – evolved as adaptations to overcome food scarcity, as Mattson writes in his book.

As evolution has it, we’ve inherited these tendencies. In short, if you’re convinced that you need to take in caloric energy to be at your best at work, think again. To perform cognitively, we don’t need caloric energy, but a high and stable level of mental energy. And that’s exactly what IF provides us with. It does so through two major mechanisms.

First, IF releases a chemical called epinephrine in our brain. At the same time, that chemical is also released throughout our body, where it has a name you’re probably familiar with: adrenaline. Similar to the “waking-up” hormone cortisol, epinephrine prepares us to become active – by firing up our sympathetic nervous system and increasing our level of alertness. This is why I like to think of epinephrine as the “alertness chemical”.

Second, IF is an excellent way for maintaining a stable level of blood glucose, which is not only great for our health, but also for our mental energy: While sharp spikes in blood glucose – as well as the dips that naturally follow them – directly lead to reduced energy levels and poorer cognitive performance, IF stabilizes our blood glucose and thus provides us with relatively high and stable levels of mental energy throughout the morning.

How to get into a fasting routine

If I got you interested in trying it out, here’s the good news: Getting into IF is easier than you might think.

Since it’s about not ingesting anything that contains calories for a specific amount of time, fasting and eating are two sides of the same coin. Even if you eat three meals a day with snacks in between, you are fasting whenever you are asleep. That’s, by the way, where the term for most people’s first meal of the day comes from: “break fast”.

If you decide to fast in the morning, drinking is even more crucial. Consider ingesting caffeine strategically in the morning and early afternoon. For many people (including myself), that substance is very effective at blunting feelings of hunger.

Even more importantly, drink plenty of water in the first 10 hours of your day. Also, consider adding half a teaspoon of salt to your first glass. Why? While many people attribute the shaky feeling they experience during IF to low blood glucose, the real cause usually is insufficient hydration and sodium. Plenty of water and a bit of salt will likely solve that problem.

On top of that, here are three important guardrails for making IF work for you:

First, avoid eating close to sleep. Panda recommends fasting one hour after waking up and three hours before bed to improve sleep. If you stay in bed for eight hours a night, that already gets you to 12 hours of fasting, which is a great start.

Second, set a target for your fasting window. Going for 16 hours is most popular. It lets you get the health benefits of IF while losing body fat and maintaining muscle. As it turns out, Hugh Jackman’s famous Wolverine diet included 16 hours of IF.

Third, approach your target fasting window slowly. Going from eating your first meal at 8 am to noon in a day, say, will only leave you overwhelmingly hungry and irritable. Instead, work up towards your target window in increments of 45 minutes per day.

TL;DR

On top of having plenty of water (and possibly some caffeine and salt) in the first 10 hours of your day, here are three tips to make IF work for you:

1) Start with IF during the first hour after waking up and three hours before bedtime.

2) Set a target for your fasting window. Ideally, that’s 16 hours (give or take 2 hours).

3) Approach that target window in increments of 45 minutes per day.

Next week, I'll delve deeper into how specific kinds (and quantities) of the food we eat impact our mental energy.

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Until next week,
Christian