clarification of metabolism in relation to atkins diet?

[dingleberry007]

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Hey everyone...

I was reviewing the metabolism pathways for biochem earlier today, and i was just wondering if someone with a better grasp could help me with this.

what is wrong with the atkins diet? it seems it shifts the pathway to fatty acid breakdown instead of using glucose so our body goes into a perpetual breakdown of fats and glycogen mode. am i missing something here?

just curious...

 

[ZonaRidicularis]

z

 

[hdu]

No glucose, so energy comes mainly from beta oxidation of fatty acids
Beta-oxidation produces acetyl CoA; most of it continues to Krebs cycle.
First reaction of Krebs Cycle: acetyl CoA + oxalacetate
Important source of oxalacetate: Pyruvate + CO2 (reaction of pyruvate carboxylase).
Important source of Pyruvate: Glycolysis.
If you don't eat glucose, where are you going to obtain glucose for glycolysis?
(Glycogen reserves only last 12 hours)
So, there is a problem with the source of pyruvate, and consequently, with the source of oxalacetate, and consequently, with the Krebs cycle.
Take in account also that pyruvate and oxalacetate formed from other metabolic pathways (like transamination) are required for gluconeogenesis (there are organs and cells that depends on glucose)
So...
Acetyl CoA accumulates and form an excess of ketonic bodies, that becomes a source of energy for extrahepatic tissues (the liver can not use ketonic bodies for energy), but the brain will need always a certain amount of glucose, red blood cells are dependent on glucose..and there is a chronic state of light or mild ketosis that is not physiologic.

I hope this brief summary helps

My blog www.biochemistryquestions.wordpress.com

 

[Monica Lewinsky]

I think the Atkin's diet is a no carbohydrate diet (right?). Since your body is not receiving any glucose it starts breaking down stored fats. People who stay on this diet for a long time eventually go into ketoacidosis b/c of ketone body production by the liver. I guess that's why it's bad.

I found one case report about the Atkins diet causing ketoacidosis, but one case report doesn't make it a "wrong" way to diet (Ketogenic diets can be used to treat epileptics). Like the previous poster said, you'll get into a state of detectable ketosis, but your body will keep the pH in physiologic range.

 

[peter90036]

there's a study in NEJM http://content.nejm.org/cgi/reprint/359/3/229.pdf

2yr lowcarb(high protein/fat, "atkins") vs lowfat or something,

outcome the lowcarb lost a bit more weight, and the serum lipids were good !