How to do safe and healthy exercise during fasting

There are many types of fasting, and each are conducted for a variety of reasons. There are short-term fasts as well as long-term fasts. Do you know that even the six to 10 hours of sleep you get each night is considered a fast? Fasts may include certain food types, juice only, water only, or no foods and liquids. Therefore, you may think the type of exercise you do will depend on the type of fasting conducted. You are correct! Below are the main fasting types and how you may exercise with each according to scientific studies.


How Much Exercise After an Overnight Fast?

Whether you realize it or not, you are naturally fasting each night when you sleep. The approximate number of hours one sleeps each night (or day if you work night shift) is 8 hours. However, you probably don't eat just before you go sleep, and you most likely don't eat as soon as you awaken. That adds a couple of hours onto your regular nightly (or daily) fast. All in all, you could be fasting 8 to 12 hours per day. The first meal of the day is called 'breakfast' as you are 'breaking' your fast.

There has been much controversy in the world of fitness on whether you should eat or not eat before exercising after awakening. Recent studies have shown that exercise is perfectly fine before any food is ingested and still within the fasted state. In fact, a scientific study has shown that exercise in the fasted state with cardio exercise increases fat oxidation up to 25 percent when performed for one hour. The study was conducted on a group of fasting cyclists and another cycling group that consumed carbohydrates during exercise. Another study reported that glucose tolerance and insulin sensitivity improved when exercising in a fasted state.

How Much Exercise with Short-Term Juice Fasts?

Short-term juice fasts usually last between one day to several days or a week. They may include only vegetables and fruits, juice, or water. Most are 'juice' only fasts. Studies were difficult to find for this particular type of fast with exercise. However, one study conducted an experiment on healthy, non-obese males. They were only allowed 150 to 300 calories in the form of vegetable and fruit drinks per day. There was absolutely no limitation on physical activity, and the test was for 8 days. This was compared to an earlier fast with limited physical activity in the same amount of time. The study concluded that free cholesterol levels had decreased. What can we take from this? It seems that unlimited activity on a very low calorie juice fat is safe and can even be healing to a certain extent.

How Much Exercise with Intermittent And Ramadan Fasting?

Intermittent fasting is a pattern of eating that alternates between periods of fasting and non-fasting. Let's go back to the 'Overnight Fast' we discussed earlier. As noted, you fast every 24 hours when you sleep for approximately 8 to 12 hours. With intermittent fasting, your fast would be a little longer within that 24 hour period. For some, it may be 16 to 20 hours while others may not eat for 20 to 24 hours. This is a long-term and ongoing fast for several weeks or months.

If you're familiar with the Muslim tradition of Ramadan, you will understand fasting a bit more. Ramadan is a time of spiritual reflection for the Muslim culture where they are to put more effort into following Islam teachings. Ramadan is set aside for 29 or 30 days every year. The Muslim faithful fast during this time without food or drink (including water). It is an intermittent fast that begins at dawn and ends at sunset each day. This is approximately 14 to 16 hours of the 24 hour day in most parts of the Muslim world, and it is conducted during the waking hours. Therefore, food and drink is limited to a very few hours each day. Muslims usually eat only two meals per day during Ramadan - one just before the breaking of dawn and then another right after sunset.

Studies have been conducted on intermittent Ramadan fasting and exercise. According to one study on Ramadan fasting, high intensity exercise should be conducted after sunset. This was determined after the effects of fasting on performance. The exams were performed at three different times of the day (8 AM, 6 PM, and 9 PM) while performing intense exercise. It seems that the body needs time to fuel itself before a strenuous workout. However, other studies concluded without specific times of day for training safely:

"Elites and professional sportsmen can continue training during Ramadan with no adverse effect on the renal function and immune and inflammatory systems. Thus, continuance of training during Ramadan can be performed safely."

"Current evidence from good, well-controlled research supports the conclusion that athletes who maintain their total energy and macronutrient intake, training load, body composition, and sleep length and quality are unlikely to suffer any substantial decrements in performance during Ramadan."

This is good news to those who want to exercise during intermittent or Ramadan fasting. We can now conclude that unlimited exercise can be done any time of day during intermittent fasting as long as your nutrition (i.e., calories and macronutrients), as well as water intake, is in tact. However, if you are practicing Ramadan and are limiting your calorie intake with only two 'normal' meals, you may want to train after sunset.