-
burning fat vs sugar (podcast feedback)
Hi Doc T
You mention that burning fat is a “cleaner” process than sugar for the mitochondria. Could you please explain that more specifically? I think you made reference to oxidative byproducts-does this mean that with each molecule of glucose that goes through Kreb’s cycle that a free radical singlet oxygen is formed? Assuming the mitochondria are the same in each cell of the body (brain versus muscle vs skin vs everything else) since they are all from the same source.
-
6 Replies
-
From what I understand, the burning of glucose is a less efficient process than burning fat (free fatty acid or FFA) in the mitochondrial electron transport chain / Krebs cycle. The FFA releases 20 to 28 times more energy than it does from glucose. And in the process, free radicals are formed from oxidizing glucose that need to be eliminated.
When there is no time for the cell to clean up the free radicals they accumulate and, according to Otto Warburg in 1932 (and the one who taught Hans Krebs), this damages the mitochondria.
I don’t go into the details because most of the members here don’t want these details but only the concept. I will admit that I too gloss over the details because I am not a full time biochemist! However, I would be interested in knowing these details. Are you able to explain how free radicals are formed and how they are removed via antioxidants and hormesis? If not, I promise I will dig into this in the near future. (Adding a note to do so on my to-do list now!)
Yes I am assuming that all mitochondria throughout the body are the same as I have not heard that they are different. I only know that the concentration of mitochondria differ in locations with the ovaries having the most per cell followed by the pre-frontal cortex of the brain, the retina and the heart muscle.
Please let me know if you want to add to this. I will also be looking into this as well but have a full plate at the moment.
-
I’ll look into it as well and see what I can find about what we know from first principles. It’s been a while (read decades) since I looked at this stuff so a refresher would be a good idea. I know on some of the podcasts you have said that burning glucose is a “dirty” process but that it’s the preferred fuel of the brain so those two things seem to conflict-why would we evolve to burn glucose in our brains if it is detrimental? Enquiring minds want to know…
-
Great point! The brain accepts glucose without the need for insulin. This is called insulin independent glucose uptake. Muscles also have this independent uptake when the cells are in exercise mode (at V O2 Max or approximately 60% of aerobic exercise – under anaerobic levels).
Glucose for the brain comes from liver glycogen storage and from gluconeogenesis of amino acids recycled from old or damaged proteins. It also can come from gluconeogenesis of lactate and another metabolite I just can’t think of right now. It is in this gluconeogenesis pathway where metformin works in reducing blood glucose.
The brain needs an unrestricted flow of fuel to survive and glucose is an easy source at anytime of life / season. However, ketones (a specific type of fat) is also a good source of fuel for the brain. It is one of the “tricks” to improving brain function and is the reason why a ketogenic diet was discovered in the 1920’s to be a beneficial diet for those with epileptic seizures. It is also the reason why adding butter (a short chain fatty acid called butyrate) and/or 8 carbon length MCT oil (medium chain triglycerides) to the morning coffee is so beneficial along with having a time restricted feeding window in the late afternoon for humans.
Horses get their butyrate from the digestion of cellulose by the colonic bacteria.
However, when sugar is fed in excess of daily needs then there are not only no ketones available but the glucose is sequestered by insulin and is driven into fat storage.This forces the horse to increase gluconeogenesis and hence is part of the reason for chronic protein deficiency (the other part is the lack of protein intake).
I hope this resolves your inquiring mind….
-
-
I understand that a healthy human microbiome can metabolize soluble fibre and resistant starch to short chain fatty acids as well. This I found fascinating.
I looked up why the brain only uses glucose as fuel and it seems that burning fatty acids (presumably via ketones) produces too many reactive oxygen species and neurons are not adept at dealing with them due to poor antioxidant apparatus within the neurons and it causes them to die. Have you read this?
-
No I have not. But I also know that if you don’t get enough sleep every night (4 to 5 sleep cycles) then these will accumulate. Poor sleep seems to be at the root of cognitive decline (called now type 3 diabetes) as well as insulin resistance. Sleep and eat well – gee, maybe mom was right? Luckily we don’t see (recognize or measure) cognitive decline in horses.
-
-
We’re deep into a biochemical soup here…for simplicity this is how I am thinking of it…short chain fatty acids are very good for the gut and are appearing to be neuroprotective to the brain but maybe the brain just doesn’t like to burn them due to the neurons’ inability to survive the byproducts. So perhaps the benefit of the SCFAs to the brain in cognition is less as a fuel and more in the aspect of improving tight junctions and possibly blocking amyloid.
And our gut microbes make them for us out of soluble fibre and resistant starch-a lovely parallel to the cellulose story in the horse’s hindgut. And yes, butter on popcorn…
Thank you for this conversation.
Log in to reply.