What happens to fat when it's burned?
- Thread starter Andy741
- Start date
Well, in the simplest terms, the by products of fat burning are water and carbon dioxide. Of course glycerides are also "released" as triglycerides are broken down. But in general terms, carbon dioxide and water are the end result of fat metabolism.
Text book answer
The oxidation (i.e. burning) of fatty acids occurs in the mitochondria. The transport of fatty acyl-CoA into the mitochondria is accomplished via an acyl-carnitine intermediate, which itself is generated by the action of carnitine acyltransferase I, an enzyme that resides in the outer mitochondrial membrane. The acyl-carnitine molecule then is transported into the mitochondria where carnitine acyltransferase II catalyzes the regeneration of the fatty acyl-CoA molecule.
The process of fatty acid oxidation is termed beta-oxidation since it occurs through the sequential removal of 2-carbon units by oxidation at the b-carbon position of the fatty acyl-CoA molecule.
Each round of beta-oxidation produces one mole of NADH, one mole of FADH2 and one mole of acetyl-CoA. The acetyl-CoA--- the end product of each round of b-oxidation--- then enters the TCA cycle, where it is further oxidized to carbon dioxide (CO2) with the concomitant generation of three moles of NADH, one mole of FADH2 and one mole of ATP. The NADH and FADH2 generated during the fat oxidation and acetyl-CoA oxidation in the TCA cycle then can enter the respiratory pathway for the production of ATP.
This is the major oxidaiton pathway for fatty acids, but there are others. These alternative pathways still yield the same final end products of fatty acid oxidation.
The oxidation (i.e. burning) of fatty acids occurs in the mitochondria. The transport of fatty acyl-CoA into the mitochondria is accomplished via an acyl-carnitine intermediate, which itself is generated by the action of carnitine acyltransferase I, an enzyme that resides in the outer mitochondrial membrane. The acyl-carnitine molecule then is transported into the mitochondria where carnitine acyltransferase II catalyzes the regeneration of the fatty acyl-CoA molecule.
The process of fatty acid oxidation is termed beta-oxidation since it occurs through the sequential removal of 2-carbon units by oxidation at the b-carbon position of the fatty acyl-CoA molecule.
Each round of beta-oxidation produces one mole of NADH, one mole of FADH2 and one mole of acetyl-CoA. The acetyl-CoA--- the end product of each round of b-oxidation--- then enters the TCA cycle, where it is further oxidized to carbon dioxide (CO2) with the concomitant generation of three moles of NADH, one mole of FADH2 and one mole of ATP. The NADH and FADH2 generated during the fat oxidation and acetyl-CoA oxidation in the TCA cycle then can enter the respiratory pathway for the production of ATP.
This is the major oxidaiton pathway for fatty acids, but there are others. These alternative pathways still yield the same final end products of fatty acid oxidation.
First the fat is broken down to fatty acids and glycerol via lipases. Then the fatty acid is activated to yield acyl CoA...then everything Bryan said. That was just covered on my biochem final 
Here's a question; was the idea of supplymenting with carnitine an attempt to speed up the rate limiting step of transferring the acyl CoA into the mitochondria, thus increasing the rate of beta-oxidation?
Here's a question; was the idea of supplymenting with carnitine an attempt to speed up the rate limiting step of transferring the acyl CoA into the mitochondria, thus increasing the rate of beta-oxidation?
D
Dianabol
Guest
Dear armitage,
1. Here's a question; was the idea of supplymenting with carnitine an attempt to speed up the rate limiting step of transferring the acyl CoA into the mitochondria, thus increasing the rate of beta-oxidation?
>>> Yes, that was probably the idea. Whether this is the rate-limiting step, I'm not sure but usually, the enzymes can be the rate-limiting step in such biochemistry. L-carnitine supplementation is a scam. The studies were done on non-human entities I think, and on humans, it just doesn't work. We could imagine a scenario where this would work but considering other factors, it would be quite far-fetched and perhaps, not practical to put oneself in a situation where the consumption of L-carnitine will have any significant effect on lipid metabolism.
Godspeed, and happy HSTing
1. Here's a question; was the idea of supplymenting with carnitine an attempt to speed up the rate limiting step of transferring the acyl CoA into the mitochondria, thus increasing the rate of beta-oxidation?
>>> Yes, that was probably the idea. Whether this is the rate-limiting step, I'm not sure but usually, the enzymes can be the rate-limiting step in such biochemistry. L-carnitine supplementation is a scam. The studies were done on non-human entities I think, and on humans, it just doesn't work. We could imagine a scenario where this would work but considering other factors, it would be quite far-fetched and perhaps, not practical to put oneself in a situation where the consumption of L-carnitine will have any significant effect on lipid metabolism.
Godspeed, and happy HSTing
Right. All human studies have failed to show any effect of high-dose carnitine supplementation on the rate of fatty acid oxidation, at rest or during exercise.[b said:
However, carnitine "might" be helpful during severe ketogenic states. This has been explored in children on ketogenic diets to fight tumor growth rates.
In general, carnitine supplments do not offer any benefit to normal "healthy" people.
Supplementation in carnitine depleted states may also be useful. THis is important for certain drugs, like sodium valproate (classed as a secondary deficiency) usually administered for hte likes of Bipolar disorder. Treatment with SV usually results in weight gain for hte patients, and some theorise that the secondary deficiency is, partially at least, the cuase of the weight gain.
There are a few trials taking place (a couple in NZ as well) on carnitine in BP patients, in the form of Lcarntine L tartrate.
I dont think there is much published yet tho, I have seen the basic setup earlier in the year, but it was boring as anything
There are a few trials taking place (a couple in NZ as well) on carnitine in BP patients, in the form of Lcarntine L tartrate.
I dont think there is much published yet tho, I have seen the basic setup earlier in the year, but it was boring as anything