This sort of thing has been tested in animal models and it doesn't work. It is also completely implausible, but that's beside the point, you are unlikely to be convinced I suppose.

There are clinical trials of fasting in cancer patients. These have been designed by careful and ethical scientists and doctors. They are looking currently at whether fasting can improve the efficacy or tolerance of chemotherapy.

It is frankly stupid to take an already malnourished individual and make them fast for 40 days.