Helen Ding
Helen Ding is an intern at Cosmos. She is a biomedical science graduate completing a master's degree in journalism at the University of Melbourne.
Can fasting improve chemotherapy response? The answer is yes – according to new research from Edith Cowan University (ECU) in Perth, Western Australia – which found that the combination of dietary restriction and exercise enhanced the effects of chemotherapy by boosting the immune response, reducing immunosuppressive factors in the tumour microenvironment and improving drug delivery.
In 2022, cancer was responsible for nearly 10m deaths, making it a leading cause of death globally.
Chemotherapy, often administered alongside surgery and radiotherapy, is a common treatment strategy where anti-cancer drugs destroy cancer cells, but can come with significant challenges, including adverse side effects and varying efficacy.
A team of researchers, led by ECU PhD student Cristino Crespo-Garcia, are exploring how fasting and exercise can help to address these challenges by improving immune function. The research has been published in the Exercise Immunology Review.
“We know that a part of the efficacy of chemotherapy relies on the immune system,” says Crespo-Garcia. “We want to evaluate the effectiveness that exercise, and a fasting mimicking-diet have on patients that are undergoing chemotherapy.”
According to the study, chemotherapy efficacy can be lost or reduced in several ways. Tumour cells can employ various mechanisms to evade the immune system or change in ways that diminish their potency to trigger an immune response. Defects in the body’s immune system, which can occur due to immunosuppressive changes in the gut microbiota, also impact chemotherapy success.
In preclinical studies on animals, dietary restrictions, including caloric restriction (reducing daily energy intake by 15–30% without macronutrient ratio changes) and various fasting regimens, appear to counteract these problems.
They report that fasting promotes autophagy in tumour cells, which increases their visibility to the immune system and attracts immune cells to the tumour area. Autophagy also facilitates killer T-cells to recognise and attack tumour cells.
“It has been shown in studies … those animals that participate in fasting have a healthier immune system with more immune cells,” says Crespo-Garcia.
During a fast, “the levels of glucose, insulin and some growth factors decrease, so our healthy cells activate protective mechanisms … and stop proliferating as much,” says Crespo-Garcia.
This “protection and maintenance mode” helps to shield healthy cells from the toxicity of chemotherapy, reducing side effects. By contrast, cancer cells – unable to adapt their high metabolic demands to the nutrient-scare environment – are more susceptible to the toxicity.
Chemotherapy and the microbiome
Exercise also helps with chemotherapeutics in a similar way. Physical activity facilitates the distribution of drugs to target tissues through increased blood flow to muscles.
Studies repeatedly show that exercise not only increases the quality of life in cancer patients but also reduces some adverse effects of chemotherapy, says Crespo-Garcia. “It would make sense that exercising would assist the body in several ways, as humans did not evolve being as physically inactive as we are nowadays.”
According to Crespo-Garcia, maintaining an active lifestyle after being diagnosed with certain types of cancers, including breast, colorectal and prostate cancer, is associated with survival rates of up to 40%.
Clinical trials, which follow on from preclinical studies showing the benefits of fasting and exercise during chemotherapy, are currently being undertaken at ECU.
