The decision of whether or not to exercise while fasting should be made on a case by case basis. To answer this question, you will have to consider the type of fast you are on as well as its duration. Exercising during the types of fasts that limit your nutrient and water intake for extensive periods of time can be damaging to your body.
Exercising While on a Religious Fast
There are many reasons why people fast. Members of various religious groups fast according to their specific traditions. Some religious fasts involve going for twelve hours or more each day without food or drink. In other cases, a religious fast involves giving up only specific foods. Religious fasts can last for a day or extend beyond weeks or months.
People who fast for religious reasons often do so as a form of religious obedience. Religious fasts are often thought to be good for both the body and the spirit. Going without food gives the digestive system a break and assists with elimination of bodily toxins. In a spiritual sense, religious fasts are considered as symbolic of sacrifice and growing closer to the higher being.
Deciding whether or not to exercise while on a religious fast has to be determined on a case by case basis. If your fast allows you to eat while the sun is down, this gives you a chance to replenish your body with the fluid and nutrients needed to sustain energy for a workout. You want to avoid situations where your workout heavily taxes your body without the ability to drink water or consume calories for adequate energy.
Fasting to Improve Health
If you are fasting as a way to improve your health, you will want to consult with a doctor to determine whether exercise while fasting is a good idea. If you are on a juice fast that involves intake of a wide range of nutrients, including proteins, your doctor may feel that exercise can be a healthy part of your regimen. You will want to avoid exercise in situations where your fast leaves you dehydrated or with low energy.
Fasting to Lose Weight and Exercise
Some people fast to lose weight. They might do this for a day or two to kick start a diet. In other cases, juice fasts for dieting purposes may extend across weeks. In these cases, the juices will contain calories intended to provide some level of nutrition while restricting calories enough to induce fat burning.
In general, you want to make sure that your diet contains adequate proteins and carbohydrates to fuel your exercise regimen. With weight loss as your goal, you do not want to risk losing muscle. Additionally, if your fast involves a complete absence of food and drinks, you risk dehydration. Water is needed for a large number of metabolic processes and is of special importance if you will be exercising.