Studies in the lab show worms, flies, rats, etc. are living much longer if they keep in controlled starvation condition.
Go hungry to cheat your brain that you are in the hardship, your cell lifespan is extended to give you more chances to produce offspring. This is probable biological reason why starvation prolongs the lifespan.
Singapore senile politician, Lim Kuan Yew practiced 70% full stomach eating habit to keep healthy body which may sound rational if lab result is applicable to human being.