But the results from human trials are not conclusive yet, and Barcellos-Hoff emphasizes that even if it has looked promising in mouse studies, fasting alone (without chemotherapy) should not be something patients attempt on their own. Especially for a patient who already has decent odds of survival, undertaking an unproved approach can be quite risky.
And although many diets and alternative treatment regimens exist, Longo cautions, "if you do it without the science, you can end up doing more damage than good." For example, when a fast is too long the immune system starts to suffer, potentially leaving a patient even less protected.
"Everything has to be timed so that it maximizes the damage to the cancer," he says. Research into that is still ongoing. Even just finding out whether fasting with chemo will be as successful in humans as it is in mice might not come quickly. "You have so many cancers and so many chemos that it's almost like a never-ending process," Longo says.