Fasting, a method of restricting food intake, has been practiced for thousands of years.

Water fasting is a type of fast that restricts everything except water. It has become more popular in recent years as a quick way to lose weight.

Studies have shown that water fasting could have health benefits. For example, it may lower the risk of some chronic diseases and stimulate autophagy, a process that helps your body break down and recycle old parts of your cells.

That said, human studies on water fasting are very limited. Moreover, it comes with many health risks and is not suitable for everyone.

Potential benefits of water fasting
Both human and animal studies have linked water fasting to a variety of health benefits.

Here are a few health benefits of water fasting.

May promote autophagy
Autophagy is a process in which old parts of your cells are broken down and recycled.

Several animal studies suggest that autophagy may help protect against diseases like cancer, Alzheimer’s, and heart disease.

For example, autophagy may prevent damaged parts of your cells from accumulating, which is a risk factor for many cancers. This may help prevent cancer cells from growing.

Animal studies have consistently found that water fasting helps promote autophagy. Animal studies also show that autophagy may help extend life span.

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.

May help lower blood pressure
Research shows that longer, medically supervised water fasts may help people with high blood pressure lower their blood pressure.

In one study, 68 people who had borderline high blood pressure water fasted for nearly 14 days under medical supervision.

At the end of the fast, 82% of people saw their blood pressure fall to healthy levels (120/80 mmHg or less). Additionally, the average drop in blood pressure was 20 mmHg for systolic (the upper value) and 7 mmHg for diastolic (the lower value), which is significant.

In another study, 174 people with high blood pressure water fasted for an average of 10–11 days.

At the end of the fast, 90% of people achieved a blood pressure lower than 140/90 mmHg the limits used to diagnose high blood pressure.

Additionally, the average fall in systolic blood pressure (the upper value) was a substantial 37 mmHG.

Unfortunately, no human studies have investigated the link between short-term water fasts (24–72 hours) and blood pressure.

May lower the risk of several chronic diseases
There is some evidence that water fasting may lower the risk of chronic diseases like diabetes, cancer, and heart disease.

In one study, 30 healthy adults followed a water fast for 24 hours. After the fast, they had significantly lower blood levels of cholesterol and triglycerides two risk factors for heart disease.

Several animal studies have also found that water fasting may protect the heart against damage from free radicals.

Free radicals are unstable molecules that can damage parts of cells. They are known to play a role in many chronic diseases.

Moreover, animal research has found that water fasting may suppress genes that help cancer cells grow. It may also improve the effects of chemotherapy.

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