It is really important that you get your hands on a good university level textbook that explains fuel utilization during exercise.
An important concept in exercise physiology is the respiratory exchange ratio. You see in it literature as R or RER. The respiratory exchange ratio or R tells us what type of fuel is being used during exercise. When we know R we have an idea of what percentage of energy is derived from carbohydrate or fat.
I did not include protein because as you are very well aware protein contributes little to total energy production during exercise.
Here is what you should know…
When R is equal to 1.00 100% of energy for ATP production during exercise is derived from carbohydrates. Fat contributes nothing. When R is equal 0.7% then 100% of the ATP produced is produced using fat as a fuel source. When R is equal to 0.85 approximately 50% of the energy comes from carbohydrates and 50% comes from fat.
You should also know that in order to get accurate respiratory exchange ratio percentages the subject being tested must have reached steady state as far as exercise intensity is concerned.
Really interesting question, I hope I was able to adequately address it, it is something you will have to study indepth but that’s the answer in a nutshell.
I could go look up the information, but so could you can you which will teach you more so I’ll give you information that will better understand the info you look up. Joanne is exactly right on RER. You can find this in any textbook and probably online, although you are pretty close with your figures.
A key thing to remember is that everyone is different. The goal is to be less reliant on carbs the higher intensity we go. This allows us to use a store everyone (including skinny marathon runners) has a lot of- fat. The longer we can keep from using glycogen the better! A good way to test this is if you (or your clients) can exercise while fasting and not have a drop in performance then they are good at burning fat. If they struggle a lot, then they are normally burning a lot of sugars when exercising.
As stated, this is a complex question. During exercise you are burning some of both sources and even some from protein. The amount depends on a number of factors. All of these factors play a different role in the energy system at different times. In a nut shell, fat takes a longer time to contribute energy and tends to be too slow to contribute in high intensity exercise the way that carbohydrates can. But fat does still contribute in all exercise to some degree.
If you are looking at this from a weight loss perspective, fat will contribute to the recovery refueling of muscle energy stores after exercise along with the post exercise fuel that you should be consuming. The body will allocate calories to go back into the fat cells if there is enough excess to cover it. Some of the fat energy is going to go into the fat cells no matter what, but if there is a calorie deficit (not too extreme), the fat cell will release some of that restored fat over the course of time.
I have really (really really) over simplified this as I don’t think I should spoon feed you everything. I do teach such topics to interested students. And this type of information is the type that I do feel can be shared in an online learning environment. You can check out my website if you think you might be interested in some of my CEC courses. I teach over a dozen topics that are already set up. But I also teach to specific request topics as needed. www.hawaiifitnessacademy.com or contact me through my IDEA profile.