Eating before a ride is obviously not a mandatory thing. However, at high levels of exertion your body will use up it's available glucose faster than your liver can produce more. This happens very quickly in the case of a 40k tt for example. You have to be careful with doing high intensity work when not properly fueled because your body will then find other fuel sources and the first choice is muscle protein. The harnessing of body proteins (typically from muscle and ligament tissue) is called catabolism. One side effect of catabolism is an increase in acidic keytones in your bloodstream. The effects of this include persistent or delayed muscle soreness, muscle damage, and weakness.

What Canaboo is saying is he's trained his body to use proteins and fats instead of sugars to fuel his workouts. While this is possible and common practice for many athletes, especially those trying to reduce body fat, it is almost never recommended due to the damaging effects of excess keytone production.

http://en.wikipedia.org/wiki/Catabolism