Exogenous Ketones: How They Help During Dieting or Exercising

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By Jill Levy

It’s thought that humans, and many other animal species, too, developed the capacity to produce ketones (or ketone bodies) in order to prolong survival during periods of caloric deprivation.

Ketones are beneficial for our muscles, brains and other tissues during times of stress — such as when we’re intentionally restricting calories because we’re fasting, cutting out carbohydrates from our diets, or doing endurance exercise.

Ketones are considered the most energy-efficient source of fuel for the body, releasing high amounts of ATP (adenosine triphosphate), which is often referred to as “the energy currency of life.” Not only can your body make ketones, but you can also acquire ketones from exogenous ketone supplements.

Exogenous ketone supplements and their select ingredients can help to amplify the many positive effects of the ketogenic diet — especially during the initial transition to a very low-carb diet.

What Are Exogenous Ketones?

Ketones are defined as intermediate products of the breakdown of fats in the body. They are made in the liver by fatty acids which you acquire from your diet.

When you follow a very-low carb, very-high fat diet — also known as the ketogenic diet — your body starts producing organic ketone compounds, which serve as an alternative fuel source to glucose from carbohydrates. Basically, the keto diet fires up your fat-burning capacity by changing the way your body utilizes energy.

Exogenous ketones are ketones supplements that come from outside the body. Ketones can be taken in various forms including: capsules, oils, powders or drinks. No matter which type you use, it should be able to help by supplying you with an immediate usable source of ketones, or fatty acids that are converted to ketones.

What do exogenous ketones do?

Generally speaking, exogenous ketones mimic the effects of ketones that are naturally produced by our bodies under certain circumstances. The liver naturally produces endogenous (meaning inside) ketones while in the metabolic state of ketosis, while exogenous (meaning outside) ketones are those provided from supplements.


The human body produces three types of ketones, and these are the same types also found in ketone supplements:

  • Beta-hydroxybutyrate (BHB) — accounts for roughly 78 percent of total ketones in the blood.
  • Acetoacetate (AcAc) — accounts for approximately 20 percent of ketones in the blood.
  • Acetone — accounts for only about 2 percent of ketones in the blood.
Beta hydroxybutyrate (or BHB) is the most abundant type of ketone that we produce, helping to provide the bulk of energy when our diets are nearly devoid of all carbohydrates. While there’s three types of ketone bodies, the ketone found in exogenous ketone supplements is usually only or mostly beta-hydroxybutyrate (BHB).

    In terms of exogenous ketones (those made outside the body), there are three main types of ketone supplements:

    • Ketone salts (sometimes called BHB salts), which are ketones that are bound to minerals, including sodium, calcium, magnesium or potassium. Ketone salts are typically the type used in powdered ketone products, which contain some combination of BHB, sodium and other ingredients.
    • Ketone esters, which are basically “raw ketones” that metabolize quickly into BHB. This type is not widely available for most consumers but is typically used in research/studies. While esters are believed to have the benefit of raising blood ketone levels quickly, they are also notorious for tasting terrible and causing unpleasant digestive issues. However, new ketone ester products are now hitting the market that claim to taste better and work rapidly.
    • Ketone oils, which can include MCT oil. MCT (medium chain triglyceride) oils are used to boost ketones and help with fat burning. They may also support training, exercise performance and growth of lean muscle mass. Coconut oil also contains medium chain triglycerides, but MCT oil is a more concentrated source. MCTs must be broken down first before they can be used for energy, making this type of supplement slightly less effective than ketone salts or esters.

    Beta-hydroxybutyrate is the most active type of ketone body, so that is the ketone that most exogenous ketone supplements aim to increase.

    Products may also contain other ingredients that support ketosis, such as bone broth, caffeine, coffee or coffee extract, apple cider vinegar, spices, collagen, probiotics and/or adaptogen herbs like ashwagandha. One example is Ancient Nutriton’s Keto FIRE formula, which features exogenous ketones, MCTs and adaptogens to boost energy levels and support a healthy metabolism.

    Because powdered ketone supplements don’t tend to have the best taste, other ingredients like cocoa, vanilla extract or stevia may be used to enhance the flavor.

    Different ketone products also vary in terms of their calorie and macronutrient content. Some contain only fat, while others provide an ideal ratio of both fat and protein with very minimal carbohydrates (this is typical of some powdered products that are used to make ketone drinks/smoothies/shakes). One advantage of using capsules and powdered ketone products is that they are easy to travel with, shelf-stable and can be mixed with other ingredients to make their taste more appealing.

    Exogenous Ketones vs. MCT Oil

    The very best foods for increasing natural ketone production are performance fats — especially MCT oil, butter, and coconut oil.

    MCT oil, such as Ancient Nutrition’s Keto FUSION Organic MCT Oil, is a very popular supplement among people following the keto diet because it can have multiple welcomed effects. It’s often used to quickly increase fat intake, boost natural ketone production and more.

    MCT oil has an advantage over exogenous ketones when it comes to cost. It tends to be less expensive than many exogenous ketone supplements.

    What are ways that you can use MCT oil? MCT oil can be taken just like a supplement, by having a tablespoon once daily. You can also add a tablespoon or more to your keto coffee in the morning, a shake or smoothie. It’s mostly flavorless but does add fattiness/creaminess to anything it’s mixed with. It tends to be easy to digest and can be better tolerated than some ketone supplements.

    Related: What Are the Best Keto Supplements?


    Exogenous ketone supplements are usually taken to boost the effects that the keto diet and intermittent fasting have to offer. Below is more about the functions and benefits associated with exogenous ketones:

    1. Can Help Support You During The Transition Into Ketosis

      You can use exogenous ketone supplements to help you transition into ketosis (the metabolic state where your body is using fatty acids for its primary source of energy) more easily and quickly, since ketone supplements supply your body with a direct source of ketones that are easily used as fuel.

      If you take a break from the keto diet (let’s say you’re carb-cycling, for example), then you can use ketone supplements for support transitioning back the diet.

      Taking a ketone supplement may help you as you enter into a keto diet and lifestyle as your body adjusts to it.

      2. Can Support Weight Management

        How do ketone supplements help burn fat? As mentioned above, they’re beneficial for getting you into ketosis. However, taking ketone supplements may not lead to weight management if you aren’t also following a very low-carb ketogenic diet.

        In other words, ketone supplements are helpful for keeping you in ketosis, but they aren’t a magic bullet when it comes to weight management. You will still need to track your fat, protein and carbohydrate intake (at least at first) to make sure you’re actually in ketosis and burning fat.

        Once you have a good idea of what it takes to stay in ketosis, you can use exogenous ketone supplements to help keep your energy up and to cope with cravings.

        You may also use exogenous ketone supplements to deepen your level of ketosis while practicing intermittent fasting, as your body begins to produce some ketone bodies.

        3. Can Promote Energy Levels

          Exogenous ketone supplements can be used to support healthy energy levels and physical performance.

          4. Help to Support a Healthy Memory and Cognitive Function

            When glucose is not available from your diet, fatty acids as well as ketone bodies can be metabolized by the brain. Ketones are known to support cognitive health by facilitating cognition such as focus, attention and more.

            5. Helps Support a Healthy Metabolism

              Exogenous ketone supplements can support a healthy metabolism, specifically when someone is also eating a generally healthy diet that isn’t high in highly processed foods.

              6. Supports a Healthy Response to Moderate Stress

                It’s thought that ketone supplementation can support a healthy response to stress, while supporting a positive mindset.

                7. Supports Exercise Performance and Recovery

                  Have you ever heard that ketosis makes it harder to perform physical tasks or work out? Nothing could be further from the truth! In fact, entering a state of ketosis may have a noticeable impact on even high-intensity exercise performance.

                  Exogenous ketones can actually support both exercise performance and muscle recovery. This could be particularly helpful for high-intensity athletes who wish to follow a ketogenic lifestyle.

                  How to Use

                  Ketone supplements can be used in between meals or before a workout to provide you with a quick source of exogenous ketones. You can also use ketone supplements to help you get back into ketosis more easily and quickly if you’ve abandoned the diet for a period of time.

                  They can be taken with food or on an empty stomach, but may be more impactful if you take them on an empty stomach (such as first thing in the morning) or when fasting.

                  If you’re using a powdered ketone supplement, try mixing one scoop/serving with about 12 ounces of water, plain almond milk, coffee or tea. Ketone drinks/smoothies can be enjoyed warm or cold.

                  Exogenous Ketones Supplementation and Serving Sizes

                  How you use exogenous supplements depends on your goals. Because there are many types of ketone products available that are used differently, always read directions and serving size recommendations.

                  • You might use exogenous ketones for about 3-5 days while you’re transitioning into ketosis. Use about 1/2 to 1 serving (such as one scoop or 3-6 capsules) per day. Another approach is to try having smaller amounts/doses spread throughout the day so your body has a steady supply of energy coming in. Depending on the type of product you use, it might be recommended that you take 1/3-1/2 of a scoop/serving at a time, several times per day.
                  • To help you while you get into ketosis, you might decide to have one scoop of a ketone product in the morning, or to use half a servings 1-3 times per day.
                  • For help with exercise performance and recovery, use one serving/scoop about one hour before a workout.
                  • If you’re taking keto capsules, a typical serving will be about 6 capsules daily with 8 ounces of water. Capsules can be taken with or without food.

                  How to Balance Ketones on the Keto Diet

                  Remember, while ketone supplements may have a number of benefits, you can still naturally increase/optimize your own production of ketones, which may have more lasting health effects. Other than taking exogenous ketone supplements, there are also dietary changes you can make and other lifestyle habits that can increase ketone production.

                  These include: eating a very-low carb, high-fat diet (aka the keto diet), fasting and doing regular exercise.

                  To really maximize ketone production and enhance effects like fat-burning, you can combine a ketogenic diet, intermittent fasting, exercise and exogenous ketones like ketone capsules, a powdered product or BHB salts.

                  Other Considerations

                  Of course, you should always consult your healthcare professional prior to embarking on any dietary or lifestyle routine.

                  If weight management is your primary goal, you’ll want to track your progress. What level of ketosis is generally best for supporting a healthy weight?

                  • The optimal range of blood ketone levels is between 0.6-6.0 mmol/L, depending on your goals. When you’re not purposefully limiting carb take, levels will typically stay below 0.5 mmol/L.
                  • Quality ketone supplement products can help increase your blood ketone levels. Following a keto diet correctly can increase levels even more. Most people on the keto diet will have ketone levels between 2-3 mmol/L. (20)
                  • For general weight management, aim to get your ketone levels above 0.6 mmol/L.

                  Be sure to drink enough water, rest and sleep enough, and to not over-exercise while you’re getting into ketosis.

                  Final Thoughts

                  • Exogenous ketones are ketones supplements that come from outside the body.
                  • Exogenous ketones mimic the effects of ketones that are naturally produced by our bodies under certain circumstances, including when following the keto diet or fasting.
                  • Benefits associated with ketone supplements include: help transitioning into ketosis, help staying in ketosis, more energy, enhanced physical performance and recovery, and support for cognitive health/mental performance.
                  • There are three main types of ketone supplements: ketone salts (sometimes called BHB salts), ketone esters and ketone oils (such as MCT oil). Ketone products come in various forms: liquid, oil, capsules, extracts or powdered mixes.
                  • You can use exogenous ketones for about 3-5 days while you’re transitioning into ketosis, have smaller amounts/doses spread throughout the day so your body has a steady supply of energy coming in, have a scoop of a ketone product in the morning to help keep side effects away, or use one serving/scoop about 30 minutes to an one hour before a workout. If you’re taking keto capsules, a typical dose will be about 6 capsules daily with 8 ounces of water. Always refer to product label directions.
                  Jill Levy has been with the Dr. Axe and Ancient Nutrition team for five years. She completed her undergraduate degree in Psychology from Fairfield University, followed by a certification as a Holistic Health Coach from the Institute for Integrative Nutrition. Jill takes a “non-diet” approach to health and really enjoys teaching others about mindful eating, intuitive eating and the benefits of eating real foods.