What Are Ketones? | Everything You Need to Know

Ketones serve as an alternative energy source for the human body, specifically our mitochondria – the ‘powerhouse’ of cells.

While it can be argued that glucose (sugar) is the primary source of energy in humans, it is not essential for our survival.

Ketones, on the contrary, are byproducts of fat metabolism in humans when carbohydrates are restricted, and are thus necessary substrates for living.

Biochemically speaking, ketones are simple, organic compounds that contain a central carbon atom bound to an oxygen atom and two carbon-containing substituents, designated by an “R” symbol (see chemical structure below).

Ketones are ‘simple’ molecules because they don’t contain any chemical groups that readily react.

Types of Ketone Bodies

In humans, three different ketones (also referred to as ketone bodies) are made in the mitochondria of the liver, including acetone, acetoacetic acid (AcAc), and beta-hydroxybutyric acid (BHB).

The image below shows the chemical structures of these three ketone bodies:

Note that BHB is not technically a ketone since it contains a reactive hydroxyl group where a double-bonded oxygen would usually be.

Nevertheless, BHB still functions like a ketone in humans and is converted to energy (via acetyl-CoA), just like acetoacetate and acetone can be; however, the conversion of acetone to acetyl-CoA is rather inefficient.

When and Why Does the Body Produce These Ketone Bodies?

Ketone bodies, specifically acetoacetate, is made from the breakdown of fatty acids. Fatty acids become a primary energy source in humans when carbohydrate intake is low.

When carbs are kept in low enough quantities long enough, the body enters a state called “ketosis”.

When ketosis takes place, acetoacetate is present in large amounts throughout the body, which can then go on to form BHB and acetone. Our body may then use these molecules for energy purposes.

Remember, when carbohydrates are low, the body needs an ‘alternative’ fuel source for survival. Ketone bodies are that fuel source that steps in and powers the body.

Naturally, during periods when food is limited (such as fasting), ketone body production also increases for energetic purposes. This is why dietary protocols like intermittent fasting might heighten the ketosis effects of low-carbohydrate diets.

Is Raspberry Ketone the same as a Ketone Body? What about 7-Keto-DHEA?

Raspberry ketone seems to be a popular ingredient in many fat-loss and general health supplements nowadays. However, despite its designation, raspberry ketone is not in the same category as ketone bodies.

Many consumers believe that exogenous ketone supplements are the same as raspberry ketone supplements, which is not the case.

Raspberry ketone is a polyphenol found in red raspberries that gives them their pleasant aroma and ruby red color.

Chemically speaking, raspberry ketone is similar to the compound synephrine and might have fat-loss benefits. However, it is not yet understood if raspberry ketone serves as an efficacious supplement for body composition purposes.

7-Keto-DHEA is a unique derivative of DHEA (dehydroepiandrosterone), a steroid produced abundantly in humans.

While DHEA is typically converted to either testosterone or estrogen, 7-keto-DHEA has a slightly different chemical structure that imparts different characteristics to the molecule.

Some supplement companies claim 7-keto-DHEA is useful for weight loss, muscle building, and delays in the aging process.

In short, raspberry ketone and 7-keto DHEA are neither ketone bodies nor are they related to ketogenic diets. They may have separate benefits, but research is still out on their efficacy as dietary supplements.

Monitoring Ketone Body Levels

People who follow a ketogenic often will utilize different test/specimens to measure ketone values in the body.

These methods typically include urinalysis, blood sampling, and breathing tests. You can do these tests through a clinic/lab, but it is much more convenient to do them at home with over-the-counter measuring devices.

Ketone levels in the body range from zero all the way up to 4 or more millimoles per liter (mmol/L). For reference, see the ranges below to determine your ketone body levels:

  • Negative ketone level: <0.6 mmol
  • Low to moderate ketone level: 0.6 to 1.5 mmol
  • High ketone level: 1.6 to 3.0 mmol
  • Exceptionally high ketone level: > 3.0 mmol

Read on for in-depth descriptions of the different methods for testing ketone body levels.

Urine Testing (Urinalysis) for Ketones

Method: Urinalysis for ketone body can be done by utilizing specific OTC thin plastic strips with a small reagent area on them. These are typically sold under the brand name Ketostix at most pharmacies.

You simply urinate a small amount onto the strip and check for any color changes that occur with the strip’s reagent. Different colors designate different levels of ketone bodies present in your urine.

Pros: Urinalysis is the simplest and most affordable means of testing for ketone bodies. Pretty much any pharmacy will have Ketostix available.

Cons: Unfortunately, urine testing for ketone bodies is the least reliable method in terms of accuracy. The longer you follow a ketogenic diet, the more adapted your body will be at utilizing ketones. In turn, urinalysis can have misleading results by coming up negative. However, for people who are newbies to a ketogenic diet, urinalysis will be useful in the short-term to measure ketone body production.

Blood Testing for Ketones

Method: Much like a diabetic uses blood glucose measuring lancets, the same method can be employed for measuring ketone bodies in the blood. Simply prick your finger and put a drop of blood on the ketone measuring strip.

Pros: This is the most accurate means of testing for ketone bodies, specifically BHB, and it’s rather simple too.

Cons: Ketone strips for blood testing are not very cost-friendly, sometimes upwards of $10 per strip. You might be able to shop around online and find them cheaper, but don’t expect to find anything less expensive than Ketostix.

Breath Testing for Ketones

Method: The Ketonix breath meter is the best tool for breath testing; it measure the amount of acetone in your breath. .

Pros: The upfront cost is a little high, but you can a breath meter for a long time so it pays off quickly.

Cons: Checking for acetone is not necessarily a reliable means of assessing acetoacetate or BHB levels in the body, so this testing method should be used in conjunction with another method.

Ketone Level Warning Signs and Myths

Excessively high levels of ketones in the body can be detrimental, particularly when reaching the point of ketoacidosis.

Ketoacidosis is when your blood becomes acidic from extremely high ketone production. This condition tends to be most common in diabetics, so exercise caution if you’re diabetic and following a ketogenic diet.

Be sure to note that ketoacidosis is not the same as nutritional ketosis, which is healthy and safe.

The majority of people won’t have to worry much about ketone production in the body while on a ketogenic diet; the body does a good job of either using or eliminating excessive ketones.

Myth: Purple Ketostix always means I’m in ketosis

Ketostix are quite unreliable for measuring actual nutritional ketosis as they measure levels of acetoacetate instead of beta-hydroxybutyrate (BHB).

Thus, Ketostix can result in false positives and “trick” people into thinking they’re in ketosis when they’re not.

Moreover, the body may excrete very little acetoacetate in the urine when you’re actually in a keto-adapted state, as BHB is the dominant ketone body produced.

This would lead to Ketostix suggesting you’re not in a state of ketosis despite having high blood BHB levels.

For a more accurate measurement of nutritional ketosis/blood BHB levels, you need to purchase a blood ketone monitor either online or from a local pharmacy.

These devices work very similarly to blood glucose monitors and require a simple finger prick to determine how many ketones are in the blood.

Myth: The darker my Ketostix, the better

If anything, having very dark Ketostix would be a sign of concern that you’re reaching a critical state of acetoacetate production in the body – which is a condition called ketoacidosis. Ketostix are relatively useless for measuring nutritional ketosis.

In fact, Ketostix are designed specifically to help diabetics avoid ketoacidosis and not for laypeople to measure BHB levels in the blood.

As mentioned the previous myth, to get a more accurate measurement of nutritional ketosis/blood BHB levels, you need to purchase a blood ketone monitor either online or from a local pharmacy.

These devices work very similarly to blood glucose monitors and require a simple finger prick to determine how many ketones are in the blood

Myth: Ultra-High Ketone Levels Are Best for Rapid Fat Loss

Ketone bodies are not inherently fat-burning molecules in the body; rather, they are a source of energy. This would be analogous to saying that having a large amount of cholesterol in the blood stream is indicative of fat burning.

However, there is some preliminary research that suggests rats eat less when they supplement with exogenous ketones, which has positive ramifications on weight loss. But the main thing to note is that more is not always better.

Ketones are either used directly by tissues or converted to acetyl-CoA, which can then be fed into metabolic pathways in the body and used for energy production.

With that being said, ketone bodies are much less likely to be stored as fat than protein and carbohydrates, and in that sense, ketogenic diets are a great way to promote weight loss and minimize excess fat gain when trying to build muscle.

In the event you did consume an exorbitant amount of ketones from supplementation (exogenous ketones), the body – specifically the kidneys – would rapidly work to filter ketones out through urine rather than converting them to fat tissue.

Again, this is not to say that you can’t gain fat if you consume an abundance of exogenous ketones (or if your body reaches an excessive level of ketone production), but that they are less prone to be converted to fat than other macronutrients.

Take-Home Message

All in all, ketones are physiologically essential for our health and well-being. Better yet, they provide a superb fuel source when carbohydrates aren’t available and can help with the fat loss process.

There’s also a large body of evidence suggesting ketone bodies are key for delaying the aging process and possibly reducing the risk of cancer.

Remember, when testing for ketone bodies, you are generally best going with blood sampling. Urinalysis through products like Ketostix can help in the short-term and for ketogenic diet newbies, but that isn’t a reliable test method in the long-term.

The good thing is that once you confirm you’re producing adequate amounts of ketones, you don’t need to recheck very frequently.

With a better understanding of the ketone bodies found in humans, be sure to check out our other content on ketosis and ketogenic dieting!


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