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Medical News Today: Can fasting help fight cancer?

Fasting may help with cancer treatment. There is a growing body of evidence supporting the role of fasting in both cancer treatment and prevention.

Some research suggests that fasting helps fight cancer by lowering insulin resistance and levels of inflammation. Fasting may also reverse the effects of chronic conditions such as obesity and type 2 diabetes, which are both risk factors for cancer.

Also, researchers believe that fasting may make cancer cells more responsive to chemotherapy while protecting other cells. Fasting may also boost the immune system to help fight cancer that is already present.

This article covers the effects of fasting on cancer treatment and prevention.

Improving insulin sensitivity

Fasting may help improve the effectiveness of chemotherapy.

Insulin is a hormone that allows cells to extract glucose from the blood to use as energy.

When more food is available, the cells in the body become less sensitive to insulin. This insulin resistance means that the cells no longer respond to insulin signals, leading to higher levels of glucose in the blood and higher fat storage.

When the food supply is scarce, the human body tries to conserve as much energy as possible.

One way it accomplishes this task is by making cell membranes more sensitive to insulin. Cells can metabolize insulin more efficiently, removing glucose from the blood.

Better insulin sensitivity makes it harder for cancer cells to grow or develop.

Reversing the effect of chronic conditions

Some research has shown that conditions such as obesity and type 2 diabetes are risk factors for cancer. Both are linked to a higher risk of multiple types of cancer and lower survival rates.

A 2017 case study looked at the effect of short-term fasting on type 2 diabetes. The participant in the study fasted for 24 hours two to three times per week.

After 4 months of fasting, the participant had a 17.8 percent reduction in weight and an 11 percent reduction in waist size.

Also, they no longer required insulin treatment after 2 months of this fasting pattern.

Promoting autophagy

Autophagy is a cellular process in which parts of cells break down for later reuse. Autophagy is critical for maintaining proper cell function, and it also helps defend cells in the body. Autophagy plays an important role in preventing and treating cancer.

Several studies in mice suggest that autophagy may prevent cancer. These studies show how lack of autophagy leads to lower levels of tumor-suppressing genes.

While lower autophagy may enable initial tumor formation, it is not solely responsible for malignant tumor growth or spread.

Improving quality of life during chemotherapy

Bald man experiencing headache and stress pinching bridge of nose.
Fasting may help reduce chemotherapy-related headaches and nausea.

Some researchers believe that fasting improves people’s response to chemotherapy because it does the following:

  • promotes cellular regeneration
  • protects blood against the harmful effects of chemotherapy
  • reduces the impact of side effects, such as fatigue, nausea, headaches, and cramps

A 2018 study found that fasting can improve quality of life in people undergoing chemotherapy for breast cancer or ovarian cancer. The study used a 60-hour fasting period starting 36 hours before the start of chemotherapy treatment.

The results show that participants fasting during chemotherapy reported higher tolerance to chemotherapy, fewer chemotherapy-related side effects, and higher energy levels when compared with those who did not fast.

Boosting the immune system to fight cancer

A 2014 study examined whether fasting produces any cancer-fighting effects in mice stem cells. Stem cells are important due to their regenerative abilities.

The researchers revealed that fasting for 2–4 days may protect stem cells against the negative effects of chemotherapy on the immune system.

Fasting also activates stem cells of the immune system to renew and repair themselves.

This study shows that fasting not only reduces damage to cells, it also replenishes white blood cells and replaces damaged ones.

White blood cells fight infection and destroy cells that may cause disease. When white blood cell levels drop as a result of chemotherapy, it affects the immune system negatively. This means that the body has a harder time fighting infections.

The number of white blood cells in the body decreases during fasting. However, when the fasting cycle concludes and the body receives food, white blood cell levels increase.


Fasting refers to not eating at all or consuming very few calories for a certain amount of time. Fasting cycles can last anywhere from 12 hours to 3 weeks.

Short and prolonged fasting periods have promising results in cancer treatment and prevention, according to multiple studies. It is currently unclear which fasting schedule produces the best results, however.

People who are curious about fasting and whether it would benefit them during their cancer treatment should consider speaking with their doctor.