Valter Longo has proved this to be true for mice, and now has human trials ongoing to determine if it's true for us too. It worked for the first 10 people, they didn't eat for two days prior to the administration of chemotherapy and felt much better.
The reason fasting helps is that healthy cells slow down their metabolism when they are not being fed, whereas cancer cells don't "care" about the health of the host enough to shut down when the host is starved, so they are still growing and metabolizing. Of our normal cells, hair follicles and GI lining are usually fast growing. Chemo selectively kills cells that are active, so fasting the patient prevents chemo from damaging healthy cells. Awesome! My only gripe with writeups on the research is that they speak of "starving" the patient for two days, and one certainly is not starving by not partaking of calories for two days. Starving is what happens when a person's reserves have already been completely metabolized, and the body starts breaking down vital tissues to maintain itself. Most of us could go at least 3 weeks before all our fat stores were gone.
Looks like your hair will still fall out and your brain may feel fuzzy, but no worries about diarrhea! And fatigue and weakness reduced by half! That's awesome.
on Longo's work