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 it sounds strange, a water fast could make you dehydrated. This is because roughly 20–30% of your daily water intake comes from the foods you eat ( 30 ).
Although there may be some health benefits to water fasting, reducing overall calories is just as effective for weight loss, and is likely to be safer. Alternatives such as intermittent fasting could have more health benefits in terms of reducing the risks for heart disease and diabetes than a long-term water fast for days at a time and may be more sustainable.
That said, there are very few human studies on water fasting, autophagy, and disease prevention. More research is needed before recommending it to promote autophagy.
Most water fasts last 24–72 hours. You should not follow a water fast for longer than this without medical supervision.
Water fasting is not safe for everyone. People who should not fast, or who should seek advice from a medical professional before fasting include older adults, those under 18, and those who:
During the fast, it is essential to drink enough water and to spread this out throughout the day. It may be tempting to drink more than usual when fasting, but this can be harmful and should be avoided.
Keep in mind, only a handful of studies have analyzed the effects of water fasting in humans. More research in humans is needed before making recommendations.