Organic chocolate hasn't improved my health yet, so lets try fasting

Upon a recommendation from a buddy in the UK, I watched a very interesting BBC Horizon episode called Eat Fast and Live Longer. Watching it on my Ipad whilst nibbling some chocolate (organic of course) I was horrified yet fascinated by the findings of this episode. Scared by the thought of following in the footsteps of my parents (both victims of cancer), I have decided to conduct an experiment of sorts and try out this 5:2 theory for at least four weeks. My husband (bless him) has agreed to do it with me in order to make things easier. Quite frankly, I wouldn't want to try eating a steak and roast vegetables in front of me whilst I am fasting so it really was the sensible decision all round. How will I feel? Will I struggle? Will I have cravings on my fasting days? Will I be cranky? Will I feel lightheaded? Is it sustainable? I'll try and report back.