Fasting and calorie restriction (CR) have been areas of interest in both prevention of cancer, as well as reducing side effects from cancer treatments. There are limited studies looking at the impact of fasting/CR and incidence of cancer, and caution must be used in interpreting these results given the studies vary in type and quality.
Fasting during the window around chemotherapy has gained attention as a possible way to reduce common side effects of treatment. The thinking is that, when nutrient intake is significantly reduced or withheld, healthy cells respond to this stress and can slow growth and shift towards maintenance, whereas cancer cells cannot. This may cause cancer cells, but not healthy cells, to experience the damaging effects of treatment.
While a few small trials show some benefit in reducing side effects of treatment, larger scale trials are needed to further assess the safety and effectiveness of this type of dietary intervention. The need for more data is a particularly important considering many patients already find it challenging to meet nutrition needs during cancer treatment.