Please explain ketosis, ketoacidosis, and ketones

According to Wikipedia, ketosis and ketoacidosis are two separate biological processes that are nevertheless linked by a substance known as ketones.

Could someone please explain to this non-science-conversant diabetic (i.e., me):

  1. what ketosis is,
  2. what ketoacidosis is,
  3. what ketones are,
  4. how ketosis and ketoacidosis are related, and
  5. whether ketosis is dangerous for diabetics (and, if so, how).

I already know ketoacidosis is dangerous for diabetics; however, I know next to nothing about ketosis. I have heard a bit about ketosis, mainly in articles/discussions about the Atkins diet, but I am very wary of anything having to do with ketones.



I’m sure someone with more medical knowledge will be along in a sec, but here’s what little I know to start.

When you eat protein, some of it gets digested for energy, especially if most of what you ate was protein. The end result of the chemical digestion is a group of compounds known as ketones. These ketones tend to be high in nitrogen because this is usually the bit of the protein that is not all that useful for energy production. Ketosis is when you have so many of these ketone compounds in your system that your body is trying to pee them out, but they are still upsetting your other metabolic functions and making you sick. Ketosis tends to involve the kidneys, since it is their job to filter the ketones out of your blood stream.

This is why you’ve heard of ketosis in conjunction with warnings about the Atkin’s diet. If someone already has some sort of kidney issue that just hasn’t made itself obvious yet, the extra stress of filtering out lots of nitrogen compounds can make them seriously ill. The Atkin’s diet is particularly bad because you are supposed to rely on protien digestion for all your energy needs. The digestion of carbohydrates does not produce ketone bodies.

Hope that helps and I hope I’m somewhat correct.

I can help with the following:

Ketones are compounds that have 2 carbon chains attached to a carbon with one double bonded oxygen. Like this.


where R and R’ are different carbon chains.

My (non-medical background) understanding is that ketosis (Atkins used the term benign diatary ketosis) happens when you are converting diatary protein to glucose just for brain energy while the body runs on fat. The body only has a limited store of glycogen, and when that is going the brain is going to need glucose. This happens when you are eating a low carb diet, either due to diet books or natural circumstance (eskimo’s old style diet).

Ketoacidosis happens in starvation mode when your body has to break down stored protein, which means muscle and the like as there is no actual storage area. Basically the body started eating itself for the glucose needed for brain function, and may also use that energy for other things is fat reserved are also out. I’m not sure the meachism, but the blood pH becomes acid during this process.

kanicbird, that’s gluconeogenesis you’re describing.

Ketoacidosis is simply high blood acidity, accompanied by high levels of ketones in the blood, generally split into two types - there’s the alcoholic flavor, which is associated with alcohol withdrawal, and the diabetic flavor, which is associated with chronically high levels of blood glucose, which should never happen in a ketogenic diet.

Cite 1

Cite 2

  1. ketosis - the production of ketones resulting from the use of stored fat by the body for use as its energy source. Typically happens during periods of starvation

  2. what ketoacidosis is - this is accelerated ketone production occuring in people with a lack of insulin (not always in diabetics!) to the point where the liver is overwhelmed and can’t metabolise them fast enough. Since ketones are acids, ketoacidosis ensues.

  3. what ketones are - these are primarily b-OH-butyrate and acetoacetate. The major ketone produced in humans is b-OH-butyrate, and the normal sequence has b-OH-butyrate being oxidized to acetoacetate.

  4. how ketosis and ketoacidosis are related - as above

  5. whether ketosis is dangerous for diabetics (and, if so, how) - the main problem, IMHO, is that it’s fraught with danger, i.e. can easily turn into ketoacidosis if they’re not careful.

Close. Amino acids.

A ketone is any molecule which has a carbon doubly-bonded to an oxygen, and is bonded to two adjacent carbon atoms. Nitrogen is not a prerequisite.

If you stop eating carbohydrates, basically your body thinks it’s starving. First thing it does is use whatever stores of glycogen are left in your liver (glycogen is a storage form of glucose). When this runs out (which happens in about a day), your body switches to metabolizing protein. If you are consuming large amounts of protein, well and good. If you’re not (i.e., you really ARE starving, your body starts metabolizing muscle…Since this is not a terribly good strategy, after a couple of days, if no glucose is forthcoming, metabolism switches to “burning” fat instead of protein. Fats are broken down to form “keto bodies,” a variety of smallish 3- and 4-carbon ketones and aldehydes which can enter the metabolic cycles which glucose used to feed. When this happens, blood levels of these “keto bodies” are elevated, and you are said to be in “ketosis”.

Note that there are other causes of this condition. I don’t know what they are, but my hunch is, they can’t be good.

OK, I’m operating on 7 year old physiology/biochem but here goes.

Energy metabolism can be thought of in two main branches – 3 carbon and 2 carbon sources. 3-C sources eventually can supply the 2-C pathway but not vice-versa. This is a little confusing, because many 2-C pathway members have more than 2-Cs but the body can only use 2 carbons at a time (like acetyl co-A).

Carbohydrates are the only place you can get 3-C supplies. Fats, though beta-oxidation, and protein and amino acid breakdown only supply the 2-C pathway. Your body can construct sugars (a process called gluconeogenesis, which makes sense), but the first material it needs to do so is a 3-C molecule called pyruvate. Pyruvate can also be stripped of a C and made into acetyl co-A, which is the main currency of the 2-C cycle, and an entrant into the Krebs cycle (which converts these 2 Cs into CO[sub]2[/sub] and gives a lot of energy out).

No protein or fat breakdown can be used to back construct sugars. We maintain small sugar reserves (in the form of glycogen), but these are easily depleted. After these are gone, we shift completely into 2-C. No more carbohydrates are made, and instead the energy metabolism shifts to ketones. This is very important for some organs, especially the brain, which can only use sugars or ketones.

Insulin is a hormone that signals that the body is fed. Sugars/carbohydrates are the “easy” form of energy metabolism, and normally the body looks for them to trigger insulin release. The cells see insulin, uptake sugar, shut off protein and fat breakdown (which is “harder” for the body to utilize), rebuild glycogen stores, and shuffle the rest off into energy metabolism and fat deposition. If you want to burn fat, you have to get rid of insulin (generally) so the cells think they are starving, which cause them to utilize what they got, which is fat and protein intake and stores and start ketone body metabolism. There are some other side effects as well, like natural appetite suppression and such, that occur once the body thinks it is starving, and the fact that sugars are not usually secreted in the urine but ketones are. This is the short of why Atkins works. Complications arise from the fact that proteins (made of amino acids) contain lots of nitrogen, and the body only has one way to get rid of nitrogen and that is through the kidney, so it puts work on the kidney. Also, if you ingest IIRC >25 g of carbohydrates, the body all of a sudden thinks it is not starving anymore and many people get an out-of-control rebound carbohydrate appetite. This is why you have to be so careful to watch carb intake with Atkins, and falling off the wagon hurts in a big way (and it can take up to 3 days or so to get the body onto full ketone metabolism).

To ketoacidosis. Mostly type I diabetics get ketoacidosis. These diabetics don’t make any insulin due to destruction of the islets in the pancreas. So cells have no signal to uptake glucose (even though there is plenty around), they think the body is seriously starving, and are radically shifted into protein metabolism (and sugar metabolism is totally shut down). The sugar remains in the blood, radically altering the osmolarity of the blood. There is a whole cascade of issues, many of which stem from the hyperosmolar state of the blood leading to dehydration and all kinds of electrolyte imbalances as glucose leaks into the urine and water and electrolytes follow. Acidosis comes from the high levels of the ketones in the blood, but the acidosis is usually less of an issue (although it is an issue) than the dehydration, electrolyte changes, and hyperosmolar state. Everything needs to be corrected in a gradual and deliberate fashion: fluids are given, electrolytes are watched closely, insulin is given slowly (often with glucose, as not to cause precipitous changes in the osmolarity of the blood), and usually the acidosis resolves itself as the kidneys and lungs catch up and start working again. Alcoholic ketoacidosis is similar, except it usually comes from an alcohol binge (alcohol is a 2-C molecule and therefore not a carbohydrate) coupled with malnutrition (so no 3-C molecules around) leading to a wave of ketone bodies that provide the osmoles that come from sugars in diabetes.