From research I have read, a reduction in calories may provide the benefit more then anything.
There is a study I found showing research mice intentionally given cancer were then put on a calorie restricted diet (often called under-nutrition without malnutrition) and it was shown that the cancer slowed, and even stopped growth.
They then introduced growth hormone to the mice, and the cancer started growing again.
CR diets have been researched for a long time, and have been shown to extend life in all animals tested so far. There is some anecdotal evidence it works in humans, yet few are willing to live on a reduction of 30% to 40% of a normal diet.
Anyway if this fast is reducing the production of Growth Hormone, which I suspect it might, that could have an effect. I personally would prefer a more balanced diet, but reduced calorically similar to the CR diets tested, and high in nutrition. I am not recommending this for anyone else, yet I would do this myself.