I am just now really studying the benefits of fasting. I have never had any problem fasting for just a day. I tried two and had no problems. Hungry more than thirsty.
I did though have a kidney stone not too long after and I am wondering if maybe the dehydration had something to do with it? I am now afraid to dry fast for more than a day since having a kidney stone is like going through the Spanish Inquisition. I am working on a Dry then Water Fast so as to not get another stone. I have learned that lemon juice has dissolving affect on a stone since they are mostly calcium. I am toying with the idea of lemon juice but i do not want to hurt the healing power of the fast.
As far as going for broke I would gradually increase the length and severity of your fasts.