Acetyl-CoA can be metabolized through the TCA in any cell, but it can also undergo a different process in liver cells: ketogenesis, which produces ketone bodies.[27] Ketone bodies are also produced in mitochondria, and usually occur in response to low blood glucose levels.[28] When glucose levels are low, oxaloacetate is diverted away from the TCA cycle and is instead used to produce glucose de novo (gluconeogenesis). But when oxaloacetate is unavailable to condense with acetyl-CoA, acetyl-CoA cannot enter the cycle, and so the body has evolved an alternative way to harvest energy from it.
Meat products make up a big part of the keto diet, but experts stress the importance of choosing quality. "Since the keto diet is based a lot on animal proteins, it's important to buy organic poultry and grass-fed, organic beef," says Aimee Aristotelous, RD. "Not only do organic selections help with limiting environmental toxins, but grass-fed options of red meats even change the composition of fats." The result, she explains, is that your body is able to better absorb those healthy fats.
If you would like to read more on ketogenic diets and ketosis, Jeff Volek and Steve Phinney discuss the new method of checking blood ketones in their book "The Art and Science of Low Carbohydrate Performance", and they also offer another good book "The Art and Science of Low Carbohydrate Living", which is a good book for those who need an introduction to the science of ketogenic diets.