There is a growing body of scientific evidence to support the health and longevity benefits of extended fasts, and this is encouraging more and more people to try it out themselves. At Zero, we consider an extended fast to mean fasting beyond 48-hours (2 days). Fasting beyond 48-hours promotes deeper ketosis, autophagy, and enhanced cell renewal, all of which have pro-longevity effects plus the potential for increased mental clarity by removing the distractions of food, and fueling the brain with ketones. Multi-day fasts can have profound effects on one's overall health and well-being, but there are several factors to consider before you decide to jump into your first extended fast. 

Tip #1: Consult with your doctor or health care professional before fasting.

People without any pre-existing health conditions are unlikely to experience any unwanted side-effects with fasting; however, it’s always a good idea to consult your healthcare professional before starting a prolonged fast. For those taking prescription medications, it’s a must. Taking medications on an empty stomach may result in unwanted side effects, and fasting may interfere with drug dosage and absorption. Lastly, for those with pre-existing health or medical conditions, fasting may not be appropriate, and you must check with your doctor to determine if fasting is safe for you.

Tip #2: Work your way up.

You wouldn't run a marathon without training for it, and you shouldn't dive into an extended fast without a little practice either. If you've spent your entire life eating every single day, you can't expect your body to know what to do once food intake suddenly halts. We recommend starting with time-restricted feeding (TRF) for those with no fasting experience. For those who are unfamiliar, this style of fasting involves restricting all daily calories to a condensed eating window, allowing for a daily short term fast, typically around 16 hours. TRF is a great way to ease into fasting and can be used to work your way up to your first 24-hour fast by shaving hours off of your eating window. Before practicing your first extended fast, try out two to three 24-36-hour fasts until you feel relatively comfortable with them. This preparation may take place over the course of a few weeks to months, but we believe it will make an extended fast significantly more tolerable. For those already familiar with short-term fasting, you can skip this introduction phase and may only need to practice a couple of 24-36-hour fasts to find your bearings. 

Tip #3: Consider a ketogenic diet before fasting.

You can achieve the benefits of fasting no matter what you eat beforehand, but you can have a major impact on how comfortable your fast is if you reduce carbs and increase fats. For maximum benefit, you can introduce a low-carb ketogenic diet 5 days before your extended fast. Both fasting and the ketogenic diet transition the body into a "fat-burning" state where fat and ketone bodies replace glucose as its primary fuel source. This is the metabolic state known as “ketosis” - thus the name of the diet. On a fast, you might start producing ketones around 16-18 hours in. It takes a bit longer on a ketogenic diet - usually 2-4 days -that's why we recommend a minimum of 5 days. It’s almost like training wheels for fasting - it mimics fasting in a lot of ways and can help prep your cells and mitochondria to better utilize fat for fuel so you’re primed to use your body's own fat stores once your fast begins. The ketogenic diet can make for a smooth transition into the fasted state, and also enhance your fasting experience by promoting adaptations that support ketosis. If you don't want to go fully ketogenic, we recommend at least tapering down carbs before your fast.

Tip #4: Schedule wisely.

Avoid scheduling your extended fast during a week full of social events -  dinner parties, lunch meetings, etc. Though you can certainly will your way through it, you’re definitely making things more difficult by surrounding yourself with temptations, peer pressure, and having to explain yourself over and over again. As far as daily tasks go, we recommend scheduling your day to the hilt - keep busy to distract yourself from food. Many people report accomplishing their best work during a fast due to elevated focus and productivity, so we recommend maintaining your regular work routine. If your fast overlaps with a free day, plan something to keep your mind occupied. The major takeaway here is to avoid sitting around with nothing to do.

Tip #5: Decide beforehand what you will consume during the fast.

While you're fasting, you will be inclined to make all sorts of justifications for why you deserve a spoonful of peanut butter or a bite of those leftovers in the fridge. To prevent you from rationalizing something irrational, draw the line before the fast. Know exactly what you "can" and "cannot" consume during your fast, so you're not deciding in a state of hunger. Depending on individual goals, some people only consume water, whereas others may allow black coffee, herbal teas, broths, bouillon, zero sugar electrolyte drinks, non-glycemic sweeteners (e.g., stevia)., and even fats (e.g., MCT oil), as examples. Make it clear what your guardrails are before you start fasting.

Tip #6: Have electrolytes on hand.

Electrolytes, such as potassium, sodium, and magnesium, play essential roles in cellular functions. Extended fasts can deplete the body of its electrolyte stores and increases the risk of electrolyte imbalances due to the suppression of insulin and loss of glycogen. Insulin stimulates sodium reabsorption, and because fasting suppresses insulin, this can cause the kidneys to excrete more sodium. The loss of glycogen also contributes to electrolyte loss, as every gram of glycogen retains ~3-4g of water. So as we burn through our glycogen during a fast, we are also burning through our spare H2O and electrolytes along the way. Some common symptoms of electrolyte imbalances include headaches, lethargy, muscle cramps, and weakness. Supplementing with 2-3 grams of sodium per day can reduce the risk for these uncomfortable side effects. You may even want to increase your sodium supplementation to 3 or 4g if you are very active. For context, there is about 1.7 grams of sodium in a teaspoon of pink Himalayan sea salt, and a little over 1 gram of sodium in a typical serving of bouillon (half a cube). Alternatively, electrolyte mixes containing sodium, potassium, and magnesium, or magnesium supplements on their own can be useful, just beware of any hidden sugar or caloric ingredients. 

Tip #7: Know what to expect.

Don’t risk getting derailed with surprise side effects. As long as you know what you’re in for, it’ll be a lot easier to push through it.  For example, you might feel a bit sluggish as you transition into the fasted state, especially if you are new to fasting and haven't quite ramped up your fat-burning metabolism. The good news is, this feeling should be temporary (it should only last the first 24-48 hours)). This probably goes without saying, but you should also expect to be hungry from time to time, though it is remarkable to feel hunger come and go without even eating. After a couple of days, you will be pleasantly surprised by the overall lack of hunger. Another common side effect is trouble sleeping. Consider a night-time routine that promotes better sleep. Our top tips are to avoid bright light and screen exposure before bed, sip on some warm water or bouillon, and try one of our Fasting Meditations to help you wind down from the day. These minor hurdles are nothing to be concerned about, but if symptoms persist for several days and you feel horrible, even with the addition of electrolytes and proper hydration, consider breaking your fast. The important message here is for you to acknowledge that a little bit of discomfort is to be expected, but you’ll want to listen to your body.

Tip #8: Have clear intentions and know your “why.”

Before you start a prolonged fast, predetermine the length of your fast. Maybe it's 3-days, maybe 7, whatever it is, set a goal, and use your Timer to track your progress. We don't recommend entering a fast without a send end point. Knowing there is a clear finish line ahead will help you stay motivated to complete the fast. Knowing why you are fasting is also very important to encourage you to keep going even when you might feel like giving up. This may also come in handy if you're stuck having to explain to others why you aren't eating. If you don't fully understand why you are fasting, then it's easy to get derailed. 

Tip #9: Out of sight out of mind

Take your temptations out of the equation. You can make your fasting experience much easier by cleaning up your default food environment. Any foods that are notoriously difficult for you to resist - get them out of the house. Donate any food that might go bad to friends and family to avoid guilting yourself into eating it. Clear the cupboards and pantry of any foods that might test your discipline. If there's nothing especially tempting around to eat, you'll have a much easier time avoiding temptation. You only have so much willpower in a day, don't waste it on resisting the urge to eat the food you see around your house.

Tip #10: Fast with a friend.

Our last and final tip: if you can find a friend to join you on your fast, we highly recommend it! This way, you have an accountability partner and someone to support you along the way. This is entirely optional, but you may find it incredibly helpful. Maybe you get together over a black coffee or sparkling water for dinner. Sharing the experience with someone else makes the fast seem less daunting, especially during your first prolonged fast. So many of our social rituals are built around food, fasting for an extended period of time can make you feel isolated. Having a fasting buddy can go a long way toward removing this psychological hurdle. 

Conclusion

If you are as compelled by the research as we are and decide to undertake a prolonged fast, these tips can help make your experience dramatically more enjoyable. Understand that while multi-day fasts can be done safely, and most people will respond well to them, it is essential that you consider any risk factors before jumping in. We can’t overstate Tip #1: consult with your medical provider to make sure fasting is safe for you, especially if you have pre-existing health issues and prescription medications.