A ketogenic diet requires that a person eat a high fat diet while keeping carbohydrates to a minimum. The third macronutrient category, protein, is an interesting one and often creates heaps of discussion. Carbohydrates and fat are primary energy sources for the body. Protein, on the other hand, is a source of essential amino acids which are the building blocks for the body. However, the amount of protein needed by each person varies greatly based upon a number of factors, including activity level, lean mass, sex, and personal preference to name a few.
One question I am often asked is, “can you eat too much protein on a ketogenic diet?”
Protein is a very satiating food, and usually the more protein a person eats, the less hungry the person is. One trick people use is to eat a diet high in protein (150 grams + per day) while limiting carbs and fat. This strategy is often wildly successful for fat loss, but it can create other problems to eat so much protein while limiting carb and fat calories so dramatically. I do not advocate eating a high protein/low carb/low fat diet, especially for women. But I do believe wholeheartedly that it is important to eat enough protein. This is even more critical on a ketogenic diet, where carbs are so limited.
Under eating protein can cause the body to lose muscle. Some argue for limiting protein because 1) doing so leads to higher ketone levels and 2) they believe that eating too much protein can lead the body to create new glucose from protein (gluconeogenesis) and keep a person from transitioning effectively to fat burning. My friend Mike Berta explains the fallacies of this thinking so well that I am sharing his post rather than recreating my own. Mike can be contacted directly at email@example.com. His Facebook group is called Ketogenic Diet for Optimal Health.
GLUCONEOGENESIS (GNG) by Mike Berta
I often hear people say “too much protein turns into sugar via gluconeogenesis.” It can sort of make sense because protein doesn’t really get stored like fat and carbohydrate does, but GNG is more complicated than this. I have spent a lot of time trying to learn as much as I can about GNG.
First off all, GNG means “to create new glucose.” It does not mean “eating too much protein turns into glucose.”
Did you know that much of what is used for GNG isn’t even protein? “Lactate, glutamine, alanine, and glycerol are the main gluconeogenic precursors in humans, together accounting for >90% of overall gluconeogenesis” (1). Lactate and glycerol have nothing to do with protein. Lactate and glycerol have to do with how triglycerides (storage form of fat) and glycogen (storage form of carbohydrate) get broken down in the body. Gerich et al. (2001) says, “Because all of the glucose released by the kidney can reasonably be ascribed to gluconeogenesis, it would appear that, if renal (kidney) glucose release accounts for 20% of overall endogenous glucose release, it should be responsible for ∼40% of all gluconeogenesis.” We should be able to say for sure that 40% of GNG has nothing to do with protein.
As far as protein goes, we have the amino acids glutamine and alanine. These amino acids exist in all the food protein sources we eat as well as on our bodies. Our bodies want to maintain a blood glucose balance, called glucose hemostasis, to ensure we do not have very high or very low levels of blood glucose.
What most people do not understand about GNG is that it is mostly demand driven when in ketosis, not supply driven. When our bodies need glucose, our bodies create glucose.
When do our bodies need glucose? Airia said it very well recently: “Gluconeogenesis is triggered by the same set of processes that trigger ketosis.” When blood glucose and insulin are low, and when glucagon is high, a demand for glucose is created. Gerich and colleagues also write, “Current evidence indicates that in overnight-fasted normal humans, gluconeogenesis accounts for about half of all glucose released into the circulation.” In other words, nutritional ketosis and fasting triggers GNG, not eating “too much protein”.
Is GNG a concern for diabetics? Yes, it is. Gerich and colleagues state, “It is well established that in type 1 and type 2 diabetes, the excessive release of glucose into the circulation is a major factor responsible for fasting hyperglycemia.” In a study of GNG in diabetics, Gannon (2001) found that 2 grams of glucose was created from 50 grams of protein from a lean steak. Two grams is not a lot of glucose from the diet. If other amino acids from that steak were converted to glucose via GNG, they did not appear in circulation in the blood. GNG is a concern for diabetics but I do not see evidence that severely limiting protein intake is beneficial.
Blood glucose does increase a small amount when eating protein, but this is not protein turning into sugar. When we eat protein, muscle protein synthesis is activated via insulin and mechanistic target of rapamycin (mTOR). These are complicated processes that are required for human life. When insulin is released, blood glucose decreases. Another hormone, glucagon, signals the liver to dump glycogen (glucose) into the blood stream to raise blood glucose back up to baseline. I do suggest that type 2 diabetics watch their protein intake so that their glucose levels do not spike more than 30 mg/dL after eating. This is not because of GNG, but it is because of the insulin/glucagon ratio creating a blood glucose spike.
Excess protein is mainly oxidized and burned for energy. This results in lower ketone levels because ketosis relies on “fat derived” fuels. The body will not create many ketones when there is an excess amount of non-fat derived energy. This does not mean that the protein you eat is turning into sugar or that you are going to be “kicked out of ketosis” for a week. This just means that protein calories still count.
Do not eat too much protein! Do not eat too much carbs or fat either.
Even in diabetics, therapeutic levels are ketones are not more important than maintenance of lean body mass. Don’t under eat protein in your chase for ketones at the expense of lean mass. Lean mass is very important and drives our metabolism. Ketones do not cause fat loss; they are the result of fatty acids being broken down in the body. You can have very high levels of ketones but eat too much food and there will be no net reduction in body fat.
Also there are good things about GNG. The process of creating new glucose is energy intensive, which means that GNG burns calories. Several studies have shown a slight metabolic advantage to a ketogenic diet of a couple of hundred calories per day. Could GNG be the reason why keto dieters might have a metabolic advantage? I say more studies are needed but it’s interesting to think about. Without GNG, we would have a dietary requirement for carbohydrate because our bodies could not create glucose.
OK, so I have presented an argument that GNG is mostly demand driven, is not all about protein and is probably a good thing. Let’s say I am wrong. You eat 100 grams of protein when you are only supposed to eat 70 grams and the other 30 grams just decides to “turn into sugar.” What happens to that 30 grams of excess protein (120 calories)? It is either used for energy within an hour or so or it is used to replenish glycogen stores.
But yes, I might be totally wrong. I’ve yet to see any evidence from actual science showing that significant quantities of dietary protein turn into glucose. We need more studies. The evidence I see shows that limitation of protein is far worse for the human body than GNG.
References and Further Reading:
http://care.diabetesjournals.org/content/24/2/382 -https://www.ncbi.nlm.nih.gov/pubmed/11238483 -http://ketogains.com/…/gluconeogenesis-wont-kick-you-out-k…/ -http://caloriesproper.com/dietary-protein-does-not-negativ…/ -http://themedicalbiochemistrypage.org/gluconeogenesis.php -https://www.khanacademy.org/…/carbohydrat…/v/gluconeogenesis -http://www.ketotic.org/…/if-you-eat-excess-protein-does-it-… -http://journal.diabetes.org/diabetesspect…/00v13n3/pg132.htm