Tips For Maximizing the Safety of Your Fasting Practice

by John Limansky, MD August 22, 2018 4 min read

Tips For Maximizing the Safety of Your Fasting Practice

Fasting is an incredibly powerful tool that can promote weight loss, heart health, improved stress management, a stronger immune system, and a myriad of other health benefits. But like most biohacking techniques, there are some important considerations and precautions you should take before beginning a fasting practice, to ensure you are doing it safely and minimizing the risk of adverse side effects. And as with any biohack, you should always consult with your physician before beginning a fast.

Who Should Avoid Fasting?

Certain medical conditions and medications can cause problems with fasting, especially extended fasts. So it’s important to discuss your plan for fasting, and any possible complications from illnesses or medications with your doctor before you begin. Certain people should avoid fasting altogether, including:

  • Children and younger teenagers
  • Pregnant women
  • Breastfeeding moms
  • Anyone with a history of eating disorders
  • Anyone with active diseases or infections
  • Athletes during periods of intense training or competition
  • Anyone recovering from surgery or major trauma

Preparing for Your Fast

Your individual tolerance to fasting will vary based on your health, energy needs, and current dietary habits. For those on typical high-carbohydrate diets, the transition to fasting can be very challenging due to the brain’s dependence on glucose for energy leading to blood sugar crashes, intense hunger, and other side effects. So it may not be possible to begin an extended fast right away. In this case it’s best to transition slowly if you are aiming to do longer fasts, by starting with shorter intermittent fasting. And when you plan to begin a longer fast, it’s best to gradually reduce your food intake for several days or a week beforehand.

The ketogenic diet mimics many of the metabolic effects of fasting, so if you are already following the keto diet, you’ll probably find the transition to fasting much easier. Many people end up inadvertently doing intermittent fasting while on keto, because the food cravings and chronic hunger are reduced so greatly. If you are looking to do some longer fasts, transitioning first to ketogenic eating can make the process much easier, especially if you are prone to frequent hunger and food cravings on a high-carbohydrate diet.

During Your Fast

Regardless of the type or length of fast your are planning to try, it’s very important to ensure your electrolyte levels are balanced, and stay balanced during your fast. Electrolytes help ensure proper hydration, support healthy organ and muscle function, balance blood acidity and pressure, regulate nerve function, help rebuild damaged tissue, and serve many other important functions in the body. Improper electrolyte levels can cause health problems including irregular heartbeat, muscle cramping and twitching, extreme fatigue, numbness, changes in blood pressure, and in more serious cases seizures, convulsions, and bone disorders. Fasting can disrupt your electrolyte balance, so it’s important to take an electrolyte supplement containing sodium, potassium and magnesium before, during, and after a fast – particularly an extended fast of more than 24 hours.

Many people will experience a little weakness, nausea, or dizziness while they are adapting to the lower energy intake of a fast. These symptoms are typically mild, and usually aren’t a sign of more serious problems. But it’s still important to be aware of your physical state, and not put yourself in situations where these side effects can lead to injury. Mild exercise is fine while fasting, but if you are feeling dizzy or weak, avoid activities where you are prone to getting hurt such as running on a treadmill or lifting weights. If you do feel these symptoms, it’s best to rest and avoid strenuous activity, and don’t drive or operate heavy machinery. And as always it’s important to maintain adequate hydration by drinking plenty of fluids.

It’s normal to feel a bit of discomfort during a fast, especially when it’s your first time fasting, or you are doing a longer fast than you’ve done before. But if it becomes too much, don’t push yourself. Listen to your body, and if you feel like you can’t continue the fast, start with a small, easy to digest meal and slowly increase your food intake from there. If you experience any serious symptoms such as racing heartbeat, fainting, vomiting, or persistent stomach pain, seek medical advice right away.

After Your Fast

With short and intermittent fasting, you shouldn’t need to take special precautions following a period of fasting. But for longer fasts of three days or more, it’s essential to reintroduce normal eating carefully. If you return to regular eating improperly, it can cause a condition called refeeding syndrome, a potentially life-threatening electrolyte, insulin, and fluid imbalance.

The first food you eat after a fast should be simple and easy to digest, such as broths, soups, fruits, and soft-cooked vegetables. Avoid indulging in dense, rich foods like dairy, fish, or meat, as the high protein and fat content can be too much for your recently fasted digestive system. It’s usually a good idea to avoid alcohol and possibly caffeine for several days as well, until you’ve gradually worked back up to your normal diet.

The quality of ingredients you reintroduce into your body is especially important, as these will become the building blocks used by your body to repair and regenerate itself. Focus on quality not quantity to optimize yourself.


John Limansky, MD
John Limansky, MD