Cellular damage due to stress is an important factor in ageing processes. It is, thus, amazing that starving, which is a stress factor per se, decelerates ageing processes and extends the lifespan of organisms. It has long been known that proteins from the sirtuin family contribute to this mechanism. To date, the exact function of the seven members of the sirtuin family in mammals has, however, not yet been clarified.
Read more here. The abstract is here
If you are interested in more on fasting as ever I'd recommend Brad Pillon's book Eat Stop Eat. You will certainly find it more understandable! Modern Forager's series What happens to your Body when you Fast is also worth checking out.