[101] Water Fasting

A science-ish explanation of the benefits and practical tips for fasting

No, it's not that crazy.

No, it's not anorexia.

And yes, you should try it, too.

Why should you fast?

For a body and mind reset: fasting can help reset your relationship with food, from both a mental and physiological standpoint, when you find yourself craving sugar and processed foods, can't seem to control portions, and go through cycles of restrict-then-binge

For weight loss: fasting is one of the most accelerated form of fat loss, while preserving muscle mass, and without the problem of "slowing your metabolism down" experienced in prolonged low-calorie diets

For mental clarity: fasting turns on certain metabolic processes in your body that improve brain functioning

For longevity and general health: fasting turns on the process of 'autophagy' which is like spring-cleaning for the body (literally 'self-eating' of dysfunctional, damaged and low-performing cells); fasting increases human growth hormone and stem cells (and new cells means more youthful looks and functioning)

How does it actually work?

In the "fed" state, your body gets energy from the food you have just eaten. Example, you eat an apple, then the body breaks it down to glucose molecules, some of which is used as fuel to power your body, the rest of which is stored as glycogen in your liver and muscles, and as fat around the body.

In the "fasted" state, your body has used up all the ‘ready-made’ fuel in the form of glycogen, so it now has to tap into the ‘storage tank’ of fat to fuel itself. Example, 12 - 16 hours after eating the apple, the body has depleted all the glycogen in the liver and muscle; and starting at 18 or so hours later, the body starts breaking down the FAT in your body to turn into energy! (think: melting the fat around your belly or muffin top!)

The average American has some 35lbs of fat in their body, which is stored fuel, a.k.a. many hours of potential fasting.

How to prep

The last supper: Instead of jumping right in, you will have a much easier time fasting if you prepare ahead. The last meal before starting your fast is especially important. If you have a HUGE carby meal (i.e., a pasta dinner followed by cake & ice cream), your body will have a ton of glycogen to go through. This stage, in my experience, is the hardest during a fast in terms of feeling hunger / desire to eat. Once the body gets into the fat-burning stage, it feels easy-breezy. So, if you eat a low-carb meal as your last meal, then your body can kick into fat-burning much sooner, as there was little glycogen to go through.

Practice: Practice makes (closer to) perfect. Longer term fasting is easier to do once you are already used to intermittent fasting (i.e., all of day's eating is done within a feeding window of, most typically, 8 hours). It would make sense that if you're already used to doing "mini fasts" of 16 hours, then it will be easier to stretch that into a longer fast.

Set a target time: Before you start, set a target. Defining a target time helps you stick through with it when things get challenging. You can try to begin with an 18 / 24 / 36 hour fast before trying a 3-day fast. I use an app called Fast Habit that is basically a timer / countdown clock. Another popular app is called Zero. If you don't want to download an app, just set an alarm on your phone for the end time.

So, what does it entail?

What to "eat" (well really, drink)!

Water: It's called water fasting for a reason. I probably drink at least 12 cups of water on a fasting day. But, the key is to not drink just plain water, because that causes more electrolyte loss. Keep reading for more on how to smarten-up and spice-up your water.

Sparkling Water: i.e., Lacroix or San Pellegrino. Helps reduce stomach "grumbles" & tastes more FUN! Beware, avoid flavored sparkling waters with sugar; stick to the "essenced" kind.

Coffee (black): It will feel good to drink something with flavor. Also helps with energy dips on the first day.

Teas (unsweetened): I prefer coffee, but I try to abstain from caffeine after 2pm. I find that black/green tea gives me a stomachache, so I generally stick to herbal teas. It also helps to drink warm liquids if you get cold towards the end of a fast.

Some annoying things that can pop up along the way

Hunger: There is a term in Korean called "belly-button clock" (i.e., My belly-button clock tells me it's noon!). It’s normal for you to feel hungry around your usual meal times. This is because your body is used to a circadian rhythm, so if you are habitually having lunch at 12pm, your body starts to expect to get food at that time. Around 12pm, as it preps itself to digest incoming food, your body will start producing digestive enzymes and a hormone called grehlin. When this happens, you will feel it as hunger. But, the good news is, this effect lasts 20-40 minutes. If you can just distract yourself for that window of hunger, you will soon realize that the hunger dissipates. Also, once your body is adapted to fat-burning for fuel, you won’t even feel the circadian feelings of hunger.

Brain Fog / Headache: This happens either if you're losing too many electrolytes, or if your body hasn't started burning fat yet. Once you get into fat-burning, headaches should subside.

Cold: If you don't have that much body fat to begin with, you might feel cold when you fast. My theory is that as the body starts burning fat for fuel, blood flow concentrates to higher-fat areas, which is why hands and feet start getting cold. Personally, I experience this starting on the second night of fasting. This is why I prefer to fast in the summer / warmer months.

Twitching: This might just be me, but I sometimes experience my eyelid twitches from the lack of magnesium. That’s when I know to supplement more electrolytes.

Sleeping: Magnesium is a precursor to the sleep hormone, melatonin. So if you have less magnesium in your body because you’re fasting, you might feel more "wired" and have trouble falling / staying asleep. I haven't found a great solution to this yet... I am considering electrolyte supplements (instead of just adding salt to my water).

Tips on How to Make it Through

Electrolytes: When your body uses glycogen stored in the liver and muscles, it loses a lot of water, (which you experience as pee) and through that process, your body loses electrolytes (i.e., sodium, potassium, magnesium). This can cause light-headedness and, in more extreme cases, headaches. To avoid this, add salt to your water (i.e., Redmond Real Salt, or sea salt). Also, San Pellegrino and Gerolsteiner sparkling waters have some built-in mineral content.

Lemon/Lime/Cinnamon/Apple Cider Vinegar: All great options to add to your water. I like to add a tablespoon of ACV, squeeze some lemon juice, add sparkling water & ice cubes! This tastes so good, feels like a mocktail, and helps me fight FOMO when the household is drinking wine.

Walk: Taking a long walk, especially around your ‘meal times’, helps your body get over the feeling of hunger. Walking also helps burn off the glycogen stores, so you can start burning fat sooner.

When NOT to do it

During your menstrual period, or the week before your period: Your body needs nourishment right now. If I fast, I usually try to do it during the week after my period.

If you're pregnant or breastfeeding.

If you're going though a really stressful time in life / work. Fasting is a stressor, so don’t over-tax your body.

If you have a bunch of happy hours / holiday parties / social engagements coming up. Obviously, you don't want to miss out on fun for fasting!


How to Break the Fast

In 2018, I made the mistake of coming out of a 3-day fast and going to a restaurant that specialized on steak / game meats. My stomach after that meal turned into a balloon, and I dealt with bloating issues from this for a while after.

Now, I follow these steps when breaking a long-term fast:

  • 20 mins before first meal: drink 8oz water with a teaspoon ACV and some cinnamon (ACV helps with stomach acid production up and cinnamon helps with insulin/blood sugar control)

  • First meal: Anything high-protein and high-fat, but low-carb. In terms of portion size, half of what you normally eat. Examples: 2 eggs scrambled in grass-fed butter, small piece of salmon, chicken, or steak. Try to avoid high-carb and sugary desserts for the first meal, you'll thank me later!

  • Alcohol: Try to avoid drinking the first 2 days after a fast. If you must, stick to clear spirits and avoid sugary mixes.


Dr. Jason Fung: He is a nephrologist and world-leading expert on fasting as a therapeutic tool for Type-2 Diabetes. He has done many podcast interviews, some of which are available on Youtube, and has published books, including: https://www.amazon.com/Complete-Guide-Fasting-Intermittent-Alternate-Day/dp/162860001

Siim Land: He is a bio-hacker and published author. Check out his youtube videos and blog: https://siimland.com/blog/