I wouldn't go near asceticism, but occasional day-long fastings do have an effect of clearing my mind. It also helps my meditation a bit, too. Helps me focus. Of course, you shouldn't fast if you don't know what you're doing. You could hurt yourself.
I have done various forms of fasting. I have never noticed being mean. Just cleansed on the inside. It seems to set me up for a deeper understanding of things, as well.