Caffeine, Sugar, and Fasting

Author: Youngjin Kang Date: April 3, 2025

For many years, I had been a lover of both coffee and sweets. I used to start every morning with a fresh cup of coffee and a morsel of glazed pastry, which I grabbed and enjoyed as soon as I got off the bed. The point of this daily routine was to kick off each day with a fresh burst of energy, aided by both the power of caffeine and an instant rush of gluten-friendly carbohydrates.

This habit, unfortunately, had an obnoxious side effect.

For the first two or three hours after the breakfast, I indeed rejoiced in the sheer sense of stimulation which it graciously provided. Endowed with the morning's initial flare of mental clarity and the fiery blessings of the sugary meal, I was able to leverage this brief period of excitement for tasks which required extra sharpness in one's mind. The hours which followed this initial phase of enchantment, however, often baffled me.

By the time the glorious effect of the morning ritual began to wear off (i.e. about 9 or 10 AM), I invariably crashed into the state of mild depression and fatigue. It was not really a surprise; after the initial spike of spiritual brightness, one could definitely expect a follow-up of the opposing effect as a counterbalancing mechanism - a combination of brain fog, anxiety, and a feeling of inner discomfort and suffocation.

Of course, if I wanted to prolong the delightful aspects of my morning ritual, I could just shove another cup of coffee down my throat in order to borrow a few more hours of productivity from my future self. And, guess what? I sometimes did exactly that, and enjoyed its short-term merit. Each time I did, though, it accrued even more "fatigue debt" in my body, causing me to become even more depressed by the time I reached the post-lunch slump (about 2PM or 3PM). And, by the time I faced this moment of mid-day crisis, I could not find a way out of it because it was too late for me to take yet another cup of coffee (If I did, it would then interfere with my night's sleep).

The problem was that, by kicking off every morning with caffeine and sugar, I was constantly sacrificing the quality of my afternoon hours for the sake of bloating the first few hours of the morning with an extra boost. It was after quite a number of years that I finally began to realize the sheer inefficiency of it.

Here was the truth. The first one or two hours of the morning did not really demand any sort of external stimuli to sharpen my mind. The reason was that the very act of waking up in the morning automatically triggered my brain to be extra alert for the first couple of hours, due to the fact that the body's cortisol level peaked by the time I woke up (Source: "Cortisol" - by Cleveland Clinic). Drinking a cup of coffee during this period turned out to be wasteful, since the sense of mental clarity offered by cortisol alone was already powerful enough to let me stay productive during that time.

Hence, injecting caffeine into my brain right after waking up also proved itself to be a bad idea for another reason. Every time I woke up in the morning, adenosine (i.e. sleep inducer) still lingered in my brain, waiting to be attached to the brain's receptors and be dissolved. Having a cup of coffee interfered with its prompt removal, since the receptors to which caffeine molecules bound themselves happened to be the same ones as those to which adenosine molecules were supposed to bind. As a result, the presence of caffeine delayed the dismissal of adenosine during the first few hours of the morning, causing them to retaliate with an attack of drowsiness after the lunch (Source: "When should I drink coffee?" - by Andrew Huberman and Andy Galpin).

Another issue was that the initial surge of energy during the early morning, promoted by an enormous amount of caffeine as well as a huge dose of simple carbohydrate, induced my energy level to skyrocket and then quickly plunge into the swamp of depression afterwards (as a means of bringing the body back to its state of equilibrium). In my experience, a rapid rise was always followed by a rapid fall.

For these reasons, I began to realize that my feastful daily habit was unsustainable and prone to emotional instability. So I decided to abandon this age-long morning ritual (dedicated to summoning the gods of Starbucks Rewards Membership) and refactor the way I approached the problem of keeping myself productive all day long.

Here is the list of solutions I came up with.

1. First of all, I stopped drinking any caffeinated beverage during the first 1 to 2 hours in the morning. This helped the adenosine to be fully dissolved before they had any chance of being sustained by the presence of caffeine, thereby preventing them from striking me back with fatigue after lunch.

2. After this initial 1-2 hour time window, I promised myself to enjoy only a mild cup of black tea instead of a thickly brewed cup of dark roast coffee. Since a cup of black tea only contained about half as much caffeine as that of a cup of coffee (or even less), it helped me stimulate my brain in moderation. After all, too much excitement wasn't even beneficial to me; it deterred me from staying focused on one thing at a time. Also, consuming too much caffeine amplified its depressing side effect; reducing the amount helped me lower the intensity of the caffeine-induced slump and stay far more productive throughout the rest of the day.

3. What about sweets? Similar to caffeine, it definitely helped me fuel my brain during the first few hours of the morning. Just like caffeine, though, it revealed its own nasty downsides after a short period of time (such as depression, fatigue, anxiety, etc). Besides, I realized that health experts do not recommend eating anything right after waking up (Source: "What is huberman saying about eating in the morning" - by Andrew Hubermann). This eventually encouraged me to begin skipping breakfast altogether, subsequently letting me exercise a mild form of intermittent fasting (i.e. at least 16 consecutive hours (per day) of not eating anything, starting from the evening and continuing all the way up to the next day's lunch).

All these 3 new habits, when practiced in combination, produced wondrous results. To be honest, it took me quite a while to get used to this new lifestyle. The lack of both caffeine and sugar during the first part of the day made me depressed at first, since I had been mildly addicted to these two stimulating substances for many years. I had to spend about a week to get used to the absence of coffee, and about 3 or 4 weeks to be comfortable with the absence of food during the initial few hours of the day. Once I fully adapted my body to this new pattern of life, however, it drastically improved the quality of my mental health (as well as physical health. See: "David Sinclair: How to Change Your Diet to Live Longer").

To be honest, I would say that the aforementioned change of habit did not give me any sort of "superpower" or anything extraordinary (I am still who I am). Based on what I have been experiencing, however, I can confidently tell that the state of my mind has become significantly more composed than before, letting me think more clearly and objectively (not just during the morning, but throughout most of the day).

Furthermore, it has been providing me with additional benefits besides psychological well-being. Abstinence from both coffee and sugary snacks helped me save money, since both of them are considerably more expensive than their healthier equivalents (especially in my country). Meanwhile, intermittent fasting helped my body regulate its blood sugar level and other aspects of metabolism way more frictionlessly than before, thus freeing me from carbohydrate addiction as well as irregular mood swings.