We were talking about gluconeogenesis, not ketogenesis.

Our last post described the evidence that the rate of gluconeogenesis (GNG) is stable under a variety of metabolic conditions. We also described several experiments in which large amounts of protein were ingested or infused and did not increase the rate. We concluded that eating more protein than your body needs probably doesn’t increase GNG.

Many of our readers expressed confusion about the implications of this finding, and our purpose in posting it.

The reason we investigated this was to address the following concern. One of the reasons keto dieters want to minimize the amount of carbohydrate they eat is so that their bodies don’t have to deal with excess glucose in the blood. Whenever we ingest carbohydrate, it becomes sugar in the blood 1. Since blood sugar must be kept within a narrow range for safety 2, eating carbs then causes the body to release insulin in order to draw sugar quickly and safely out of the blood and into storage (as fat tissue) 3.

In our opinion, the ideal situation is to introduce no significant amount of sugar into the blood by eating, and instead allow the body to supply the blood with just the amount of glucose it needs by producing it at a slow and steady rate through GNG. This is achieved by keto dieters who carefully count any carbohydrates they eat, with the goal of keeping them below a certain level, for example, 25g per day.

Because some people have said that when you eat protein above basic requirements it turns into sugar, the question some dieters have is whether they need to count excess protein toward their carb counts 4. They want to know if eating an extra 30 grams of protein means that they have added some 20 grams of sugar into their bloodstreams that now has to be dealt with just as if they had eaten 20 more grams of carbohydrate. This is the conclusion we were setting out to deny. Protein you eat in excess of your needs does not become extra blood sugar, unless you are severely diabetic.

However, this does not mean that eating too much protein has no adverse effects, or that keto dieters should be unconcerned about excess protein intake! In particular, there is another important reason that keto dieters minimize the carbohydrate they eat — to increase the levels of ketones in the blood. So a second question, and one that we did not address in the last post, is whether excess protein inhibits ketogenesis, the production of ketone bodies. In contrast to the situation with gluconeogenesis, we suspect protein does inhibit ketogenesis. If so, that’s a valid reason for not eating more than you need.


1 Evidence type: authority
Marks’ Basic Medical Biochemistry: A Clinical Approach. Michael
A. Lieberman, Allan Marks. Lippincott Williams & Wilkins, Apr 21, 2008.
p. 479

The major carbohydrates of the diet (starch, lactose, and sucrose) are digested to produce monosaccharides (glucose, fructose, and galactose), which enter the blood.

2 Evidence type: authority
Marks’ Basic Medical Biochemistry: A Clinical Approach. Michael
A. Lieberman, Allan Marks. Lippincott Williams & Wilkins, Apr 21, 2008.
p. 483

(Emphasis in original)

[I]nsulin and glucagon maintain blood glucose levels near 80 to 100 mg/dL, (90 mg/dL is the same as 5mM), despite the fact that carbohydrate intake varies considerably over the course of the day.

3 Evidence type: authority
Human Biochemistry and Disease. Gerald Litwack. Academic Press, Jan 4,
2008. p. 583

The anabolic effects of released insulin, after glucose is sensed by glucoreceptors of beta cells, are to cause the uptake of glucose and amino acids from the blood into muscle, and the uptake of glucose from the blood to form triglycerides in fat cells.

4 Evidence type: observation
Protein turns into glucose if you eat too much?!!

So I am trying to research a bit over the interwebs about just how much protein is to much and at what point your body will convert protein into glucose but there are so many different opinions on this… *pulls her hair out* This is where i think Calories in vs. calories out makes more sense… what yall think?

Is there a rule of thumb to what the bodies tipping point is for when it will convert protein into glucose?

How much protein can you eat before it turns to glucose?

muffin_maiden: I’ve read before that eating too much protein at once can cause it to turn to glucose, but how much protein can you eat before that happens?

I tend to eat two larger meals (or one big one) during the day with between 10 and 16 ounces of protein at a time. Would that amount turn to glucose or are we talking that you’d have to eat a LOT of meat before that happens?


redtoile: Thanks for this post. I worry about this all the time.


CarolynF: According to Dr. Atkins, it is around 52 percent of protein gets converted to glucose.

So, if you overeat protein at each meal, it will act like carbs.

14 replies
  1. Anonymous
    Anonymous says:

    Yap! In your article I have seen so many things that is looking for. As a health conscious person it is intelligent job to eat more protein than your body needs probably doesn't increase GNG. If you give me details more information in the next content I will be happy. Thanks for sharing nice topic.
    fat loss cure

  2. Anonymous
    Anonymous says:

    Thanks for the follow-up! Does this mean you'll be blogging more than once a month? If not, I'll take what I can get. 🙂

  3. Mitch
    Mitch says:

    I second that emotion; Blog more! This is the best written sicency blog i have ever read. I love the format your references take. If only peer review research used that reference format. one can dream right?

  4. Anonymous
    Anonymous says:

    "However, this does not mean that eating too much protein has no adverse effects, or that keto dieters should be unconcerned about excess protein intake!"

    I'd enjoy seeing a post on the adverse effects of too much protein, beyond potentially inhibiting ketosis. Things like risk of kidney damage, inhibiting mTOR and autophagy, causing bone loss, increasing cortisol, possible elevated homocysteine….separate the fact from the fiction. Just a thought.

    Anyway, nice job on the blog!

  5. Amber Wilcox-O'Hearn
    Amber Wilcox-O'Hearn says:

    Hello, healthhammer.

    There is definitely much to write about on protein, and we'll get there eventually. It's part of the plan. See "About Us" for why we haven't finished yet. 🙂

    I like that you've made a concrete list of requests. That's helpful in two ways: both to know what you're interested in, and to give us leads. I hadn't heard the homocysteine argument, for example.


  6. pantograph
    pantograph says:

    This is all very interesting. I would welcome an explanation of what happens to excess protein. Is it just excreted?

    Also, perhaps you could tell us why excess protein is converted to blood glucose in severe diabetics, but not others.

    Thank you very much,

  7. Stephen Ferguson
    Stephen Ferguson says:

    This is great stuff. As a T2 <25g keto-dieter I have observed that my blood ketone levels can dramatically decrease in response to excess protein, although I have never observed an increase in BG levels (unsuprising considering the timescales involved for GNG).

    For me the influence of protein on GNG is key, without eating lots of dairy, it's hard for me to construct a keto-diet that isn't high in protein. Eating lots of meat would be much easier.

  8. Zooko
    Zooko says:

    Thanks for the comment, Stephen Ferguson. That's interesting: you observe your blood ketone levels to fall but your blood glucose levels stay the same, when you eat lots of protein? Are you measuring your blood ketone levels with a handheld meter that uses those damned expensive $2 strips?

  9. Joe
    Joe says:

    Stephen, I'm trying to limit protein intake as well but haven't used dairy. One thought is high fat ground beef? I'm a bit on the extreme side perhaps, but find 75% ground beef raw quite edible and that naturally limits protein. Other options are bone marrow (quite yummy) and coconut oil. I've been using bone marrow, but have gotten tired of buying large amounts of bones and pushing out the marrow bit myself. Too much work.

  10. Esmée La Fleur
    Esmée La Fleur says:

    Also, I have found that in order for my body to digest the protein I consume, I NEED to eat a certain amount of fat with it. For example, if I eat hard cheese by itself, I will burp it up for hours afterwords and feel really lousy. But, if I eat it in a 1 to 1 ratio (ounce to ounce) with butter, I digest it fine and experience no digestive distress. I have the same experience with raw ground beef. If I eat lean grassfed ground beef by itself, I will experience digestive distress and feel terrible for hours. but if I add an ounce of butter per 4 ounces of ground beef, then it digests perfectly fine. I never understood this until now. I think it is my body's way of regulating my protein intake. If I eat the amount of fat needed to help me digest the protein, then it is harder to over-consume the protein because satiety kicks in sooner. Anyone else notice this?

  11. PhilT
    PhilT says:

    My thought would be "insulin" – there's an insulin response to eating protein, and elevated insulin inhibits ketone production.

  12. L. Amber Wilcox-O'Hearn
    L. Amber Wilcox-O'Hearn says:

    Well, we know that in keto dieters glucose goes up in response to protein, but I/G ratio and thus probably glucose production stays the same. (This is discussed one of the subsequent articles… Protein, Gluconeogenesis, and Blood Sugar) So, since the amount of glucose rises, and if it is indeed true that production is the same, it seems rate of uptake into cells must go down. So one hypothesis I have is that eating protein on keto increases uptake of something else (protein?), thus slowing down glucose uptake. But I haven't checked the plausibility of that. It's just an idea.

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