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What are Ketone Bodies?

Published February 27, 2019 (Revised: January 24, 2020) Read Time: 4 minutes
Ana Reisdorf

Written By: Ana Reisdorf, MS, RD

Ana is a Registered Dietitian Nutritionist with 13-years of experience in the field of nutrition and dietetics

ketone-bodies
<script type="application/ld+json"> { "@context":"http://schema.org", "@type":"BlogPosting", "author": { "@type": "Person", "name": "Ana Reisdorf, MS, RD" }, "publisher": { "@type": "Organization", "name": "Warrior Made", "logo": { "@type": "ImageObject", "url": "https://www.warriormade.com", "image": "https://d1ghrtdbdq2gkr.cloudfront.net/media/public/2020/01/ketone-bodies-thumbnail-0091.jpg" } }, "headline":"What are Ketone Bodies?", "datePublished":"2019-02-27", "dateModified": "2020-01-24", "description":"What are ketone bodies? We explore these natural substances and explain their function.", "image": "https://d1ghrtdbdq2gkr.cloudfront.net/media/public/2020/01/ketone-bodies-thumbnail-0091.jpg" } </script> <script type="application/ld+json"> { "@context": "https://schema.org", "@type": "FAQPage", "mainEntity": [{ "@type": "Question", "name": "What are ketone bodies and when are they produced?", "acceptedAnswer": { "@type": "Answer", "text": "Ketone bodies or “ketones” are acidic substances that the body makes from stored fat when there isn’t enough glucose available to support energy needs." } }, { "@type": "Question", "name": "What is the function of ketone bodies?", "acceptedAnswer": { "@type": "Answer", "text": "The function of ketone bodies is to provide an alternative energy source when there is not enough glucose available. Their role is really to keep your energy stable, so your heart keeps beating and your brain keeps working." } }, { "@type": "Question", "name": "Are ketone bodies dangerous?", "acceptedAnswer": { "@type": "Answer", "text": "Although there are some mild side effects of switching into ketosis, there's a lot of misunderstanding about ketone bodies and their safety. It's true that they can cause serious problems if allowed to build up to an extreme amount. But in the right amount they're not dangerous because they're present all the time in varying amounts." } }, { "@type": "Question", "name": "What does it mean to have ketone bodies in your urine?", "acceptedAnswer": { "@type": "Answer", "text": "Once the body has used up the ketones or does not need them any more for energy, they will be excreted in the urine. The presence of ketone bodies in the urine is called ketonuria." } }] } </script> <article> <div> <ul> <li><a href="#section1">What Are Ketone Bodies And When Are They Produced?</a></li> <li><a href="#section2">What Is The Function Of Ketone Bodies?</a></li> <li><a href="#section3">Side Effects Of Ketone Bodies</a></li> <li><a href="#section4">Are Ketone Bodies Dangerous?</a></li> <li><a href="#section5">Endogenous Vs. Exogenous Ketones</a></li> <li><a href="#section6">What Does It Mean To Have Ketone Bodies In Your Urine?</a></li> <li><a href="#section7">Ways To Test For Ketone Bodies</a></li> <li><a href="#section8">Ketone Bodies And Your Diet</a></li> </ul> </div> <section> <p>The main nutrient the body uses for energy is glucose from the carbohydrates we eat. Glucose provides fast-acting energy that the body can use easily for fuel. </p> <p>But, there are downsides of relying on glucose for energy. Glucose can’t be stored in large quantities. So, if the body wants to run exclusively on glucose, this means you have to eat frequently to keep your energy levels up. </p> <p>Luckily, your body is smarter than that; the body can use fat for energy in the form of ketone bodies. Ketone bodies allow you to fast for longer periods, so you are not tied to refueling every few hours to keep your energy up. </p> <p>Converting stored fat into ketone bodies does take a bit more effort than using glucose, which is why it isn’t the body’s first choice. Let’s take a look at how the body uses fat for energy and the pros and cons of doing so.</p> </section> <hr class="divider-50 divider-medium mx-auto"> <section id="section1"> <h2>What are ketone bodies and when are they produced?</h2> <p>Ketone bodies or “ketones” are acidic substances that the body makes from stored fat when there isn’t enough glucose available to support energy needs.<sup><a target="_blank" href="https://www.ncbi.nlm.nih.gov/pubmed/14769483" rel="nofollow noreferrer">1</a></sup></p> <picture class="lazy-load"> <source data-srcset="https://d1ghrtdbdq2gkr.cloudfront.net/blog-content/3-ketone-body-types-0091.webp" type="image/webp"> <source data-srcset="https://d1ghrtdbdq2gkr.cloudfront.net/blog-content/3-ketone-body-types-0091.jp2" type="image/jpf"> <source data-srcset="https://d1ghrtdbdq2gkr.cloudfront.net/blog-content/3-ketone-body-types-0091.jpg"> <img src="https://d1ghrtdbdq2gkr.cloudfront.net/blog-content/3-ketone-body-types-LR-0091.jpg" class="img-fluid" alt="ketone body types"> </picture> <p>There are three ketone bodies: </p> <ul> <li>Acetone</li> <li>Acetoacetate</li> <li>Beta-hydroxybutyrate</li> </ul> <p>There’s almost an unlimited amount of energy available in our fat cells. </p> <p>Whenever the body is low on glucose, it can tap into those energy stores and make more energy. This process of breaking down fat to make ketone bodies is called ketogenesis.<sup><a target="_blank" href="https://www.ncbi.nlm.nih.gov/pubmed/6122545" rel="nofollow noreferrer">2</a></sup></p> <p>You may not know this, but the body uses ketone bodies as fuel on a regular basis. There are even some tissues that prefer to run on ketone bodies.<sup><a target="_blank" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5313038/" rel="nofollow noreferrer">3</a></sup></p> <p>Your body will use ketones when you are on a low-carbohydrate diet, when you are fasting (even overnight), during pregnancy, or after an intense workout.</p> <p>For example, after an overnight fast, 2 to 6 percent of the body’s energy comes from ketone bodies; after a three-day fast 30 to 40 percent of energy is coming from ketone bodies.<sup><a target="_blank" href="https://www.ncbi.nlm.nih.gov/pubmed/10634967" rel="nofollow noreferrer">4</a></sup> This is a great system that allows the body to tap into the fat stores any time it needs energy and why a keto diet is so useful for sustained energy.</p> <p>Once your body switches completely into using mostly ketone bodies for energy, this state is called ketosis. Ketosis is the goal of the <a target="_blank" href="https://www.warriormade.com/content/diet/a-beginner-guide-to-the-keto-lifestyle/" rel="noreferrer">low-carb ketogenic diet</a>. <sup><a target="_blank" href="https://www.ncbi.nlm.nih.gov/pubmed/17332207" rel="nofollow noreferrer">5</a></sup></p> </section> <hr class="divider-50 divider-medium mx-auto"> <section id="section2"> <h2>What is the function of ketone bodies?</h2> <p>The function of ketone bodies is to provide an alternative energy source when there is not enough glucose available. Their role is really to keep your energy stable, so your heart keeps beating and your brain keeps working, even without food.</p> <p>Our organs use ketone bodies for energy. The first organ that will always be prioritized is the brain, because it is the most important organ in the body.<sup><a target="_blank" href="https://www.sciencedirect.com/science/article/pii/B012227055X006635" rel="nofollow noreferrer">6</a></sup></p> <p>When the body is able to rely primarily on ketones for energy in the <a target="_blank" href="https://www.warriormade.com/content/diet/how-long-does-it-take-to-get-into-ketosis/" rel="noreferrer">state of ketosis</a>, many report an improvement in brain function and overall physical energy. This is because the body is able to tap into the unlimited amount of calories stored in its fat cells, resulting in limitless energy with no need to refuel.<sup><a target="_blank" href="https://www.ncbi.nlm.nih.gov/pubmed/26892521" rel="nofollow noreferrer">7</a></sup></p> </section> <hr class="divider-50 divider-medium mx-auto"> <section id="section3"> <h2>Side effects of ketone bodies</h2> <p>When the body starts to switch into ketosis and produce ketone bodies, you may experience some side effects of this metabolic shift. This is commonly called the “keto flu.”<sup><a target="_blank" href="https://journals.sagepub.com/doi/abs/10.1177/088307380101600901" rel="nofollow noreferrer">8</a></sup></p> <p>Symptoms of the keto flu may include:</p> <ul> <li>Headaches</li> <li>Fatigue</li> <li>Brain fog</li> <li>Irritability</li> <li>Weakness</li> <li>Dizziness</li> </ul> <p>These symptoms are not due to the ketone bodies, but to the hormonal and metabolic shift that is occuring as you start eating a lower carbohydrate diet.</p> <p>Once your body adapts, after a few days, this should resolve. Drinking enough water, <a target="_blank" href="https://www.warriormade.com/content/diet/keto-electrolytes/" rel="noreferrer">taking electrolytes</a>, and taking exogenous ketones can help.</p> </section> <hr class="divider-50 divider-medium mx-auto"> <section id="section4"> <h2>Are ketone bodies dangerous?</h2> <p>Although there are some mild side effects of switching into ketosis, there’s a lot of misunderstanding about ketone bodies and their safety. It’s true that they’re acidic substances that can cause serious problems if allowed to build up to an extreme amount.</p> <p>As previously mentioned, ketone bodies in the right amount are not dangerous because present all the time in varying amounts. Under normal circumstances, ketones are part of the body’s day-to-day function and are not dangerous. </p> <p>Under very specific circumstances, ketone bodies can become dangerous. When insulin is extremely low due to uncontrolled diabetes, alcoholism, or starvation, glucose cannot enter the cells. </p> <p>Low insulin causes the body to produce large amounts of ketone bodies because your body thinks it is starving, which it is on a cellular level. Since insulin is low, it is not there to stop ketone body production.</p> <p>Ketone bodies are acidic and when they are left unchecked, they can alter the body’s pH balance. This state is called metabolic ketoacidosis. The blood becomes acidic due to too many ketones. </p> Symptoms of acidosis include:<sup><a target="_blank" href="https://www.diabetes.org/diabetes/complications/dka-ketoacidosis-ketones" rel="nofollow noreferrer">8</a>, <a target="_blank" href="https://www.ncbi.nlm.nih.gov/books/NBK493179/" rel="nofollow noreferrer">9</a></sup> <ul> <li>Confusion</li> <li>Vomiting</li> <li>Respiratory Distress</li> <li>Coma</li> </ul> <p>If allowed to continue, this can become extremely dangerous and lead to death if not medically treated. </p> <p>There is no reason to fear ketone bodies. Ketoacidosis is rare and can only happen when insulin is extremely low. This means that without insulin problems, ketone bodies pose no danger.<sup><a target="_blank" href="https://www.nature.com/articles/ejcn2013116#ref8" rel="nofollow noreferrer">10</a></sup></p> </section> <hr class="divider-50 divider-medium mx-auto"> <section> <picture class="lazy-load"> <source data-srcset="https://d1ghrtdbdq2gkr.cloudfront.net/blog-content/exogenous-ketones-0091.webp" type="image/webp"> <source data-srcset="https://d1ghrtdbdq2gkr.cloudfront.net/blog-content/exogenous-ketones-0091.jp2" type="image/jpf"> <source data-srcset="https://d1ghrtdbdq2gkr.cloudfront.net/blog-content/exogenous-ketones-0091.jpg"> <img src="https://d1ghrtdbdq2gkr.cloudfront.net/blog-content/exogenous-ketones-LR-0091.jpg" class="img-fluid" alt="exogenous ketones"> </picture> <h2 id="section5">Endogenous vs. exogenous ketones</h2> <p>As we have discussed, ketones are produced naturally by the body. But you may have noticed that you can actually purchase ketones as a dietary supplement. </p> <p>The ketones made naturally in our bodies are called endogenous ketones; “endo” means coming from the inside. Ketones coming from outside the body are called <a target="_blank" href="https://www.warriormade.com/content/diet/exogenous-ketones/" rel="noreferrer">exogenous ketones</a>; “exo” means coming from the outside.<sup><a target="_blank" href="https://www.frontiersin.org/articles/10.3389/fphys.2017.00848/full" rel="nofollow noreferrer">11</a></sup></p> <p><a target="_blank" href="https://www.warriormade.com/6-week-challenge-offer/keto-support/" rel="noreferrer">Exogenous ketone supplements</a> usually contain acetoacetate and/or <a target="_blank" href="https://www.warriormade.com/content/diet/bhb-exogenous-ketones-and-the-keto-diet/" rel="noreferrer">BHB</a>. There are two main types of exogenous ketone supplements found on the market:</p> <ul> <li>Ketone salts. BHB combined with an amino acid or mineral salt like sodium, potassium, or magnesium.<sup><a target="_blank" href="https://www.ncbi.nlm.nih.gov/pubmed/28750585" rel="nofollow noreferrer">12</a></sup></li> <li>Ketone esters. A liquid form of acetoacetate or BHB bound to an ester. They are not quite as effective at raising ketone levels as the salts but are commonly used to improve athletic performance.<sup><a target="_blank" href="https://www.ncbi.nlm.nih.gov/pubmed/28398950" rel="nofollow noreferrer">13</a></sup></li> </ul> <p>Exogenous ketones are marketed as a ketosis “hack.” By increasing the ketone levels in your blood by using a supplement, they can help you <a target="_blank" href="https://www.warriormade.com/content/diet/how-long-does-it-take-to-get-into-ketosis/" rel="noreferrer">get into ketosis faster</a>. They may also help decrease some of the uncomfortable symptoms of the keto flu. </p> <p>One thing to note about exogenous ketones: they won’t help you stay in ketosis if you don’t change your diet. They will not help you lose weight or provide any health benefits of ketosis without dietary changes. </p> </section> <hr class="divider-50 divider-medium mx-auto"> <section id="section6"> <h2>What does it mean to have ketone bodies in your urine?</h2> <p>Once the body has used up the ketones or does not need them any more for energy, they will be excreted in the urine. The presence of ketone bodies in the urine is called ketonuria.<sup><a target="_blank" href="https://www.ncbi.nlm.nih.gov/books/NBK247/" rel="nofollow noreferrer">11</a></sup></p> <p>For a person with diabetes, the presence of large amounts of ketones in the blood may be an indication of more severe problems and should be medically evaluated. </p> <p>For those following a keto diet without any insulin issues, the presence of ketones in the urine just means you are in ketosis. </p> <p>The <a target="_blank" href="https://www.warriormade.com/content/diet/how-to-measure-ketosis-with-a-home-ketone-meter/" rel="noreferrer">guidelines for ketone body levels in the urine</a> are:<sup><a target="_blank" href="https://www.diabetes.co.uk/diabetes_care/testing-for-ketones.html" rel="nofollow noreferrer">12</a></sup></p> <ul> <li>Not in ketosis: less than 0.6 mmol</li> <li>Low to moderate: 0.6 to 1.5 mmol - starting ketosis</li> <li>High: 1.6 to 3.0 mmol</li> <li>Very high: greater than 3.0 mmol</li> </ul> <p>This scale can vary depending on the type of test strips you use, so use the numbers provided by the specific test.</p> <p>If you’re just starting out on a keto diet, measuring your urine ketones can help you see if you are in ketosis and adjust your diet accordingly. Testing first thing in the morning will help you get the most accurate result.</p> <p>Although testing your ketone levels with urine strips is easy and cost-effective, they are also the least accurate way to test for ketones. The results can be skewed by hydration status, medications, and the time you have been in ketosis, so using other options such as a blood test may be a better way to test for ketones.<sup><a target="_blank" href="https://care.diabetesjournals.org/content/26/suppl_1/s106.full" rel="nofollow noreferrer">13</a></sup></p> </section> <hr class="divider-50 divider-medium mx-auto"> <section> <picture class="lazy-load"> <source data-srcset="https://d1ghrtdbdq2gkr.cloudfront.net/blog-content/testing-ketone-bodies-0091.webp" type="image/webp"> <source data-srcset="https://d1ghrtdbdq2gkr.cloudfront.net/blog-content/testing-ketone-bodies-0091.jp2" type="image/jpf"> <source data-srcset="https://d1ghrtdbdq2gkr.cloudfront.net/blog-content/testing-ketone-bodies-0091.jpg"> <img src="https://d1ghrtdbdq2gkr.cloudfront.net/blog-content/testing-ketone-bodies-LR-0091.jpg" class="img-fluid" alt="testing ketone bodies"> </picture> <h2 id="section7">Ways to test for ketone bodies</h2> <p>Like we just mentioned, there are several ways to accurately test your ketone levels. An accurate, but more expensive, way to test for ketone bodies in your blood is to use a blood glucose meter. Many have the ability to measure ketones in addition to blood sugar. But, if you do not have diabetes, these meters will not be covered by insurance and can be very pricey.<sup><a target="_blank" href="https://www.sciencedirect.com/science/article/pii/S0956566304005470" rel="nofollow noreferrer">14</a></sup></p> <p>A newer option for testing for ketone bodies is to use a breath meter. One of the ketones the body makes, called acetone, is excreted through the lungs.</p> <p>The meters have the ability to measure how much acetone is on your breath and tell you if you are in ketosis.<sup><a target="_blank" href="https://new.hindawi.com/journals/bmri/2014/869186/" rel="nofollow noreferrer">15</a></sup> Breath meters will run you about $50, but their accuracy is not as good as a blood test. </p> <p>For most people, eating a keto diet for weight loss or for the health benefits, urine strips are probably enough to know if you are in ketosis. If you are not seeing the results you are looking for while eating keto, then you may want to consider other testing methods. </p> </section> <hr class="divider-50 divider-medium mx-auto"> <section id="section8"> <h2>Ketone bodies and your diet</h2> <p>Although the body uses ketones regularly for energy to some extent, in order to switch completely into ketosis, you have to change your diet. This will mean cutting back on carbs to “starve” the body of glucose, forcing it to start relying on fat instead.</p> <p>The amount of carbs you need to eat to get into ketosis will vary from person to person. In general, a ketogenic diet involves eating between 20 to 50 grams of carbs per day.<sup><a target="_blank" href="https://www.ncbi.nlm.nih.gov/pubmed/17332207" rel="nofollow noreferrer">16</a></sup> If you are extremely active, you may be able to eat more carbs than this and stay in ketosis. </p> <p>After about a week of strict carbohydrate elimination, the body will naturally start to use ketones for energy. After two weeks, you will begin to feel less hunger and more energy from the ketone bodies you are producing. </p> <p>The bottom line is ketone bodies, under normal healthy conditions, are pretty useful. They sustain our energy while we are sleeping or fasting, so we don’t have to wake up in the middle of the night to eat. Switching to using ketones for energy can help your body use up stored fat and eat fewer calories helping you achieve your weight loss goals.</p> </section> </article>

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