Following up from the question Are carbohydrates an essential component of human diet? I am interested in knowing more specifically how carbohydrates, fats and proteins are linked in the mammalian diet.

For example, cats and other obligate carnivores eat mostly protein, so I imagine that protein has to be converted first to fat and then to glucose and other carbohydrates that the body needs. Does that mean cats are in a state of ketosis constantly? Do cats have special metabolic tuning to optimize on this metabolic pathway?

Human variations seem to suggest that such tuning exists. For example, (historic) eskimoes when fed carbohydrates tend to be especially likely to suffer from obesity and diabetes. This would suggest that their bodies are tuned to exist on protein and fat. What is this tuning?

  • $\begingroup$ What makes you think that cats consume mainly protein? $\endgroup$ Jul 18, 2016 at 19:50
  • $\begingroup$ @AlexDeLarge The way that my cats growl at me if I try to take meat away from them. $\endgroup$ Jul 18, 2016 at 19:53
  • $\begingroup$ But meat does not mainly consist of protein. Adult cats have a 26% (dry weight) protein maintenance minimum. $\endgroup$ Jul 18, 2016 at 20:03
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    $\begingroup$ @AlexDeLarge Did you read the web site you just linked? It says a typical steak has 36g of protein and 7g of fat and 0 carbs. If we exclude bones, the typical mouse is made of 85%-95% protein and 15%-5% fat (depending how fat/starving the mouse is). Human athletes have less than 5% body fat, sometimes as little as 2%. All the rest is bone and protein. $\endgroup$ Jul 18, 2016 at 20:06
  • $\begingroup$ Oh, yeah, you might be right. I actually did not think about that the non-protein parts could mainly have zero nutritional value. ;) $\endgroup$ Jul 18, 2016 at 21:15


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