In some of the earlier studies of dietary restriction in animal models, researchers measured resistance to stress as a way of predicting potential impact on lifespan and health. Successful resistance to short-term stress caused by reduction in calories typically correlates with longer life and better health. Researchers have also found in some models that fasting for relatively short periods of time – or months of dietary restriction – actually enhanced normal cells’ resistance to stress, but did not have an effect on cancer cells.
Based on these observations, Longo and colleagues hypothesized that they could use this “differential stress resistance” induced by fasting to reduce chemotherapy-related stress on normal cells, without jeopardizing the treatment’s efficacy for killing cancerous cells. Initial results in mice were encouraging: the mice survived and the chemotherapy was still effective. A subsequent but still very preliminary clinical study showed that patients who fasted in conjunction with chemotherapy reported fewer side-effects without loss of efficacy. The clinical study has been expanded to an early phase clinical trial.
Raffaghello L, et al. Fasting and differential chemotherapy protection in patients. Cell Cycle 2010 9: 4474 – 4476.
Lee C, Longo VD. Fasting vs. dietary restriction in cellular protection and cancer treatment: from model organisms to patients. Oncogene 2011 30: 3305 – 3316.
Scientific American has an article about it here: Fasting Might Boost Chemo's Cancer-Busting Properties.