I've come across this in The Paleo Solution book, but now I'm debating this with a chemist who says it's just not true.
I've found a couple of references to this but only in conjunction with drinking alcohol and being in a fasting, ketogenic state.
Anyone have anything on this?
Any literature or studies confirming this? What byproducts of ketosis are halting the conversion of amino acids to carbs?
Humans have an absolute requirement for blood glucose. If you are eating zero carbs, you would go into a coma and die if you were incapable of producing blood glucose via gluconeogenesis.
A more accurate statement would be that ketosis greatly reduces gluconeogensis relative to the early stages of a transition from high carb to low or no carb. For the first few days/weeks, your body will try to make up the carb loss via GNG, but as you adapt to using ketones this will tail off.
It won't ever stop completely, because some tissue in the body can't ever make the switch.
Since this is basic physiology I think wiki works as a source:
I've now found the part of the book you're referring to - as I recall, gluconeogenesis is the process that creates the initial ketone byproducts in the first place. Once begun, the breakdown of the triglycerides provides necessary glucose - as the amount needed is vastly reduced by ketosis. However I think this would only apply in full ketosis which can take weeks. I don't think gluconeogenesis gets switched off just like that - it would be a more gradual down-regulation in the absence of dietary protein. I'm not sure if that's what Robb was referring to though.
According to Lyle McDonald, ketosis slows down gluconeogenesis as soon as tissues like skeletal muscles are adapted to use ketones instead of glucose. This happens at the final stage of starving (day 4 or later). Before that, gluconeogenesis is even higher as the liver breaks down proteins to compensate lack of glucose if no dietary carbohydrates are present.
But GNG is never stopped completely as even in deep ketosis the brain needs about 25% of its fuel as glucose.
Read more at “The Ketogenic Diet: A complete guide for the Dieter and Practitioner” by Lyle McDonald.
I've not heard of this. Gluconeogenesis can lower ketones. The system seems to be set up to be preferential to carbs, and if you have a lot of extra protein around, it tends to increase insulin levels. I think that messes with ketone levels as well, but I am not totally clear on that part.
The quote seems backwards, unless he is describing a particular situation.