Intermittent Fasting

I've read a lot about this on my travels. Intermittent fasting is where you just don't eat for 16 or 24 hours and then follow your usual eating habits. Allegedly, this puts your body into a state of ketosis - where you use your body fat for energy. I find myself inadvertently doing this after bad days. Today I didn't eat until 3pm from 9pm the previous day. I'm not hungry, so I don't eat. I do occasionally listen to my body. Yesterday, however, it wanted me to eat doughnuts... I ignored it.