Water fasting is a period when a person eats no food and drinks only water. Fasting in this way may help with weight loss, but is it safe, and do the effects last long-term? People may undertake water fasting to lose weight, for spiritual or religious reasons, or to try and combat particular health problems. Research suggests that occasional fasting may help with weight loss, although other methods may be more effective long-term. To make sure that water fasting is done safely, people should prepare properly and choose a good time to go without food, when the body does not require too much energy.
What is water fasting?
A water fast is when a person does not eat and drinks nothing other than water. There is no set time that water fasting should last for, but medical advice generally suggests anywhere from 24 hours to 3 days as the maximum time to go without food. Throughout history, people have undertaken fasts for spiritual or religious reasons. But, water fasting is now popular in the natural health and wellness movements, often alongside meditation.
People with risk factors for certain diseases could benefit from short-term fasting. These include:
- heart disease
- high blood pressure
- high cholesterol
- being overweight
These risks are often related. When the body does not have access to carbohydrates, which are its preferred source of energy, it will use fats. So, a fast can result in weight loss as the body uses up fats in the body for its energy. According to the Academy of Nutrition and Dietetics, the best way to lose weight is to take it slowly, combining a healthy diet with exercise. It is also important to try and change some eating habits, such as reducing the number of sugary foods and snacks eaten.
Although there are potential health benefits to fasting, there are considerable risks if a fast is carried out for too long, or by someone whose health or age puts them at risk of damage to their body. If someone has health concerns, or is planning to fast for longer than 24 hours, they should seek the advice of a medical professional and consider undertaking a fast under supervision. Water fasting will not be safe for everyone, and should not be undertaken by older adults, those under 18, or those who are underweight.
An alternative to long periods of fasting can be intermittent fasting. This means eating nothing or very few calories for a certain amount of time and then eating as usual for another set period. An example is the 5:2 diet, where someone eats a regular diet for 5 days in the week, and a quarter of their daily calories on the remaining 2 days.
In a studyTrusted Source comparing intermittent fasting and eating an ongoing low-calorie diet, both methods were found to be equally good for weight loss, as well as reducing the risk of cancer, diabetes, and heart disease. Intermittent fasting was found to be as easy to stick to as a low-calorie diet.
ResearchTrusted Source based on studies with mice and rats suggests that fasting may protect against certain diseases, such as diabetes, and has the potential to delay aging. Fasting regularly for short periods of time has been associated with lower rates of diabetes, a lower BMI, and a reduced risk of coronary artery disease in people being tested for blocked arteries.
There have not been extensive human studies on fasting, although researchTrusted Source has found some positive impact on blood pressure, body weight, and improved rheumatoid arthritis symptoms from small studies. Fasting can have adverse effects on the immune system for older adults, so individuals should seek medical advice on whether occasional water fasting could be beneficial.