I read about this in Bicycling Magazine. The rationale is that caffeine causes our bodies to burn fat faster which is why they recommend two cups of espresso (or caffeinated beverage).
I've been doing this about 3x per week without realizing it was some sort of diet. I just get sick if I eat breakfast too early and I don't wake up extra early to eat unless I am going out for more that 60minutes. I have lost weight but I don't know if that is because I am cycling more or doing the "bonk diet" three times per wk. Time will tell, I suppose.