Right, true starvation mode is when your body starts catabolizing your muscles and organs because you have no fat. It means you're on the verge of literally dying. Fats seem to think the physical sensation of hunger means their organs are starting to break down. But, intermittent fasting does trigger a few different responses that have beneficial effects. One is a temporary increase of human growth hormone; another is overall increased insulin response. There are many studies suggesting that calorie restriction lengthens your lifespan. I almost never eat breakfast, so I fast from 6pm to 12pm without trying. A few years ago I frequently did 1, 3, and 5-day fasts: I really liked the results (cured a GI upset) but it's hard to go longer than a day if you work full time.