If chemotherapy wasn't bad enough, cancer patients might one day be asked to cut back on calories to help fight the disease.
Two new studies have shown that combining chemo with fasting can significantly increase the number of cancer-killing T-cells in the body - at least in mice.
Researchers at the University of Southern California fed cancer-stricken mice a low-sugar, low-protein, high-fat diet with "the benefits of starvation without the negative side effects". Six weeks of this low-calorie diet, combined with chemo, saw tumours shrink twice as much as those in mice who only got the drugs.
"The biggest factor exposing cancer cells to the T-cells is the effect on the enzyme heme oxygenase-1, which is normally at high levels in cancer cells," says cell biologist Valter Longo. "Fasting reduces oxygenase levels and gives rise to a number of changes, that included the increase of tumour-killing cytotoxic T cells."
Meanwhile in France at the Centre de Recherche des Cordeliers, scientists gave mice hydroxycitrate, a drug which tricks the body into thinking it's being starved while it isn't. It's often found in human weight loss medicines.
They had similar results to the scientists in California, seeing the mice's bodies create more white blood cells.
Dr Longo says fasting would have been a regular thing for our ancestors, and could be a "tool" the body uses to reboot the immune system and keep a lid on cancer cells.
"This coordinated, multifaceted effect seems too good to be true," he says. "It may not be a coincidence, but a very precisely evolved process that is meant to get rid of bad cells."
He's now testing the chemo-fasting strategy in humans, while the scientists behind the French study are looking into whether weight-loss drugs like hydroxycitrate could help breast cancer patients.