I think you are mis-interpreting the fat burning concept. It’s not about reducing calories. Its about increasing the fat content of the diet to stimulate fat preference in fuel utilization, not about caloric restriction. Once that adaptation occurs (that’s where the argument is right now - does it really happen or not), then the need for calories from exogenous carbohydrates is reduced and therefore the need for high caloric input is reduced (as a byproduct of using the stored fat versus glycogen from sugar conversion). So its not really caloric restriction, more like substrate utilization shift. You are not dropping the calories to allow the fat to burn, you are training your system to burn fat first regardless of how much sugar is available. If it does not need the sugar, then you can reduce the input accordingly. It works for some people better than others and depends highly upon the intensity of the training and racing you plan to do. I would not see the concept being very useful for International distance racing or even some fast HIM events, however when you get into IM and ultra-distance cycling/running, there is some evidence (not case studies, more n=1 stuff) to suggest there may be something worth looking at.
There is no disagreement in the field about whether you can alter substrate utilization through dietary manipulation or not. Even Louise Burke (the largest proponent against increased fat utilization) et al. agree that you can influence fat oxidation etc. The question is whether it improves performance.
The short answer is no, it does not. You will not run of bike faster because of increased fat oxidation. There has been much research into this area. Ultimately fat oxidation is limited and it just cannot provide enough energy for higher levels of exertion. One particular flaw, however, is that it is mostly centered around distances such as 10K, which leads us to the “Moderate Answer”.
The moderate answer is that we know it doesn’t make you faster, however, it may help you slow down less. This may be achieved by focusing substrate utilization on fat, which is in abundance for all of us, allowing the sparing of glycogen stores. If this were to be beneficial it would be beneficial in events with very monotonous, low to moderate, intensity levels. If you event requires a high power output (whether sustained like a 40k TT or surges like a road race) then there is no benefit.
The long answer is that perhaps by training low and racing high you can get the best of both worlds. There may be increased mitochondrial biogenesis through increased stimulation of PCG-1a in a low glycogen environment. You’ll feel like crap. Your training intensities will be low. However, if used as an appropriate tool (Like intervals, Base rides etc) you may be able to use dietary manipulations to improve mitochondrial function and hence performance. Often, most people get this wrong and do more harm than good, which is why I rarely fully describe how to do it or give advice that people ought to do it.
I mean this with no-disrespect…but can you state that in much simpler terms…that went way over my head.