Question asked by Robert Martin 366 days ago
What is the actual percentage of fat vs. sugars burned during different exercise intensity's?
What percentage of fats and sugars are burned at aerobic threshold vs. anaerobic threshold?
Aerobic Threshold 75% fat/25% sugar?
Anaerobic Threshold 25% fat/75% sugar?
Answers (2)
Answered by Joanne Duncan-Carnesciali
365 days ago
ExpertMemberVerified
2
Hello Robert,
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.
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.
0
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.
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.

Don't forget about the minority of people with super fast metabolism! I don't like to exercise while fasting because my body can't afford to lose any fat. A man's body needs 2-5% fat to survive and stay fertile plus extra for exercise. Women need 10-13%. My current goal is to increase from 6% to 8% to give me more energy. For this reason I like to burn more sugars not fat.
Comment by Andrew Halligan 204 days ago




