Two weeks of fasting and Z2
Recently, I embarked upon a two-week fast to kickstart some weight loss. In this article, I will recap my methods, experience, and results so that it might help others who are interested in following. Previously, I was used to fasting frequently 1–2 days/week, even 5 days/quarter, and 2 weeks once 2 years ago. As usual, do not try this at home without consulting your doctor.
I fasted between February 13th — 26th 2023. The rules were simple: at most around 500 calories/day, no Twitter, and 5 hours/week of Zone 2 heart rate training. I am not going to justify why 500 cal/day: practitioners like Valter Longo and Jason Fung have written enough about how this will not negate most of the beneficial effects of fasting. (There is also at least one observational study where low-calorie fasting still found a lot of benefits.) Last word on the subject: unless during episodes of extreme famine (which almost nobody except monks will voluntarily undergo), do you believe that our ancestors ran into the complete absence of food? The key is to approximate famines while preserving psychological and physiological safety. You don’t want to end up doing what David Blaine did, which was not only to establish a record, but also emulate torture rather than mere fasting: no food, no exercise, no bathroom — unsustainable.
Anyway, what did I eat over those two weeks? Looking at my log, it was mostly vegetable purees (green, leafy vegetables; no fruits), 1–2 scoops/day of collagen (~70 cal/scoop), plenty of Americanos (no milk or sugar), teaspoons of fermented vegetables (stuffed olives, sauerkraut, kimchi,) 1 tbsp/day of high-fat mayo (~100 cal/tbsp), 1 avocado/day (~250 cal), and/or bone broth (either store-bought or homemade) — subject to ~500 cal/day. On one occasion, I had an appetiser of goat organs in curry while meeting a friend from out of town for dinner. On the whole, I did not feel hungry although I felt like eating something solid after a week, but I had largely lost my appetite in the second week, so much so that I was able to watch an entire season of Hell’s Kitchen, and spend 1.5 hours shopping for replenishments I did not end up using during the second half. When done right, prolonged fasting can act like natural bariatric surgery: the last time I did it, it took me a fairly long time to be able to eat much again, though that was not as much the case this time.
At the same time, I wanted to make sure that I exercised during this fast. While I had lifted weights during 1–2 days fasts — including once during a 5-day fast, which I do not recommend — and walked almost every day during my last 2-week fast, I had not exercised as intensely as I did during this fast: 5 hours/week of Z2, which was done by walking sometimes (e.g., from Brooklyn to Manhattan), and mostly indoors on a gym bicycle. You can see that the second week was harder than the first: less in frequency, and higher in intensity. Was this due to physiological stress from prolonged fasting, or that my body was not yet efficiently ketone-adapted despite the long fast (and apparently high levels of acetoacetic acid in urine)? Anyway, what I can tell you is that I often felt fatigued, and light-headed when I stood up (probably a mild version of POTS), towards the end of my fast. I call BS on that whole “keto mental clarity” thing some people rave about: sure, I was able to think and work, and I think the body does prepare you to keep “hunting” or “foraging” for food during famine, but it wasn’t some magical, mystical experience. I made sure to get enough sleep by taking enough melatonin every night (2 x 3mg), and I sometimes had to take naps to cope.
Last but not last, I also abstained from all social media, especially Twitter, at this time. In fact, we Tamils have a tradition we call மௌன விரதம் (“fast of silence”). The double whammy of fasting from both food and social media gave me so much free time that I ended up using it to do something I had not recently: write a bit more. (I also became a bit more productive than usual at work, but don’t tell my bosses that.) This episode made me realise and remember that social media — like cryptocurrencies and AI — is the modern Maya.
I broke my fast by going to dinner with friends. Remembering refeeding syndrome (including the David Blaine episode with Ensure), I avoided carbs, sugar, and fats at first, and started with protein (not that Nature thinks in terms of macronutrients, but you get the idea). Then I graduated to different types of food without a hitch, but I have since been cooking and eating Paleo at home.
OK, so who cares about all this — what were results like? Well, I got what I was looking for: my weight (abdominal circumference also dropped by an inch), blood sugar (glucose-ketone index was generally below one half while fasting), and blood pressure (back to around normal) all appear to have lowered. I got my blood tested at the end of my fast, and results then were generally better than before (my PCP sees nothing wrong); I will get tested again next week to compare after refeeding. Finally, I plan to sustain all this with more intermittent fasting, Paleo, Z2, and weightlifting. I hope more people will consider fasting as a safe, time-tested, natural alternative to bariatric surgery or anti-obesity drugs, which are likely to be less beneficial, and have more side effects.
