In the low-carb community, the concept of gluconeogenesis (GNG) has become quite controversial.
First of all, let’s talk about terminology: gluconeogenesis (GNG) is the generation of glucose from non-carbohydrate substrates, including amino acids, glycerol, and lipids, to name a few examples. Essentially, your body does not require you to eat carbs in order for there to be glucose in your bloodstream. If you eat less very little carbohydrate on a daily basis, your body will manufacture glucose, usually from stored glycogen. This is nature’s way of preventing hypoglycemia, and it works very well.
Here is where things start to get controversial. Nutritional ketosis generally involves a macronutrient intake comprised mostly of healthy fats with moderate protein consumption and very low in carbohydrate. Many ketogenic low-carbers restrict protein intake to approximately what their body needs to maintain muscle mass, and they avoid regular consumption of protein in excess of those needs; in contrast to other low carbohydrate diets (think Atkins), keto is not generally considered to be a high protein diet. While the body can store extra fats and extra carbs, the body cannot store extra protein, so the working theory is that excess proteins must necessarily be dealt with through another mechanism and may be converted to glucose. Makes sense so far, right?
Enter the Controversy
There are some sub-groups of low-carbers who do not restrict protein. Some go so far as to say that GNG is a myth. Others, more reasonably, will state that while studies do show that GNG affects diabetics, it does not affect non-diabetics.
This is interesting, indeed. Studies do show that GNG affects obese people and diabetics, in that excess protein produces measurable spikes in blood glucose levels, although this same effect has not been observed and quantified in non-diabetics that are not obese.
What Does This Mean?
In a diabetic (like myself) insulin does not work properly; whether your diabetes is Type I (insulin insufficiency) or Type II (insulin resistance) there is a disordered insulin response that marks the disease, making the body less capable (or incapable) of regulating blood glucose in a healthy way. In non-diabetics, insulin will do its job and counter-balance any increased supply of glucose into the bloodstream.
Think of the glucose to insulin response as a water faucet with two separate handles, one controlling hot water and the other cold water. Let’s say that I have a stream of lukewarm water coming out of the spout, and I increase the supply of hot and cold water equally and simultaneously. The water temperature will neither increase nor decrease. Does this mean that there was no increase to the supply of cold water? Does it mean that the increased supply of cold water is a myth? Not at all. There was, indeed, an increase to the supply of cold water. It’s just that there was an equal measure of hot water to balance it out.
Now imagine that the cold water represents glucose, and the hot water represents insulin. GNG increases your supply of glucose, like our cold water example above. If you are non-diabetic, your insulin (the hot water) will balance it out. Since protein is insulinogenic (which just means it causes an insulin response), people with normal metabolisms don’t usually have to worry about a blood glucose spike, because their "hot water" balances things out. If you are diabetic or insulin resistant, however, your “hot water” is not working properly, and you will be able to notice, measure, or even feel the increased supply of glucose in your blood stream because the insulin response and your body's insulin receptors aren't working properly to balance it back out. While we absolutely need protein, this is- at least partially- how excess protein can be so problematic for diabetics.
Supply and Demand
To further compound the controversy, many people tend to disagree as to whether GNG is driven by supply or demand. Essentially, if GNG is supply-driven, this means that whenever GNG can happen, it will happen, whether the body requires glucose or not. On the other side, if GNG is demand-driven, this means that GNG will only happen if and when the body requires glucose.
There are studies that demonstrate both theories; some studies show GNG is demand driven in normal people, but others (as linked above) show that for the diabetic, the obese, and the insulin resistant GNG is at least partially driven by supply. Subsequently, both theories have merit, but I see no reason to believe that both are exclusively true. Evidence seems to point to both theories as being partially true: GNG is both supply and demand driven, depending on the substrate.
Let Me Explain
GNG can convert several substrates into glucose, as noted above. If the body is able to store the substrate (lipids, glycerol, etc.), then GNG has no reason to happen unless the body needs glucose. In these cases, GNG is absolutely demand-driven. However, GNG can also occur with excess amino acids. Not all amino acids. Extra amino acids. According to current study on amino acids, the body cannot store them, and so it follows the body must convert them to something (those somethings are keto acid and urea, the former of which can then be converted to glucose and/or stored as body fat). In that case, GNG is supply-driven.
Stating that GNG is supply-driven is partially correct. Stating that GNG is demand-driven is also partially correct. It depends on the substrate, and whether or not the body is able to store it. Some things are just converted to glucose, even if the body does not require them.
A non-diabetic with a healthy metabolism would likely not experience a large spike in blood glucose from some excess of amino acids, since any increased supply of glucose would be counter-balanced by normally functioning insulin. A diabetic or insulin resistant individual, on the other hand, is not only going to convert more excess amino acid into glucose, their insulin response will not be able to sufficiently deal with the excess glucose, hence the consistent rises in blood glucose we see in these individuals when they consume too much protein.
This is not to say that GNG is the bogeyman, that excess proteins must be universally feared, or even that GNG is the sole explanation for increased blood glucose in those with abnormal metabolisms who consume large amounts of protein. Non-diabetics generally have no need for concern. However, diabetics are a different story, and the documented increase in GNG in people with diabetes and insulin-related diseases and the obese does at least provide a partial explanation for why it is wise to moderate protein intake.
Concerning Chocolate Cake
In some quarters, it has become popular to emphatically state that “protein does not become chocolate cake.” The idea is that eating extra protein doesn't equate to the same kind of physical response as eating a slice of chocolate cake. And of course it doesn't. That's obvious to all.
It's unfortunate, but this pithy slogan has morphed into a message universally declaring that none need fear GNG, because GNG either doesn’t exist or it doesn’t affect you that much. Unless you’re diabetic. Which is about 30 million people just in America, which is a little under 10% of the population. That’s a lot of people, and the number is growing quickly every year.
The Straw Man in the Room
The analogy about the chocolate cake is popular and, like many popular things, it’s flawed. It falls into a category of logical fallacy called a “straw man fallacy.” Basically, if you don’t like a concept, you don’t attack the concept itself. That would require too much thought. No, you create a caricature of the concept- the aforementioned straw man- make the caricature look as goofy as possible, and proceed to attack said caricature.
Obviously, nobody believes in the caricatured argument that protein becomes chocolate cake because it's silly. However, science does show that the body cannot store extra protein, and that excess protein can be converted to glucose and is done so at a higher rate in diabetics, the obese, and the insulin resistant. Not all protein. Excess protein. Not chocolate cake. Glucose.
A Polite Request
On behalf of diabetics everywhere, I ask that you please refrain from stating loudly and publicly that GNG is a myth. You might believe it with all your heart. You also might not be diabetic, and GNG might not affect you that much. Good for you! Congratulations!
The evidence- anecdotal and scientific- shows it does affect people with diabetes and some other metabolic disorders. The belittling of people who do watch protein as quacks who think their steak will turn into chocolate cake is extremely unhelpful to the almost 10% of the population with disordered metabolisms.
Mockery of the concept of GNG by stating that “protein does not turn into chocolate cake" is an unjust dismissal of the very valid (and often medically crucial) concerns of people who are more affected by GNG, and for whom excess protein does cause measurable blood glucose spikes that have to be dealt with. It's not much different from sitting down next to a blind man and making fun of people who can’t see the sunset like you can. We all agree that behavior is rude and inconsiderate. Even if that is not your intention, automatically dismissing GNG concerns has the same effect. Considering how individual bodily responses seem to be, and how experimental and misunderstood ketogenic living is, there really isn't any reason people in the community should behave in such a condescending way towards others whose ketogenic experience is different than yours.
If you are not diabetic, I respect you. If you are in the high protein crowd, fine. That might work well for you, and I’m glad for you if that’s the case. High protein does not work for everybody. I happen to be in the group of people that get better results when I eat 1.0 - 1.5g of protein per kilogram of lean body mass. We’re different. No need to argue. Do we question things? Yes – absolutely! This is how science advances. But if we are to advance science, please question the actual logic, and refrain from insults and straw man arguments.