Is dietary fat burned before stored fat on a ketogenic diet?

By Dr. Stephen Phinney and the Virta Team

Certain fats, like medium-chain triglycerides found in coconut or MCT oil cannot be stored in body fat, so whatever is consumed must be promptly burned for energy. This means that if you’re adding these fats on top of your dietary fat consumption for satiety, this type of fat takes priority.

For regular dietary fats, once they are digested, they enter the circulation and participate in what is called ‘fatty acid turnover.’ Whether fed or fasted, the body is always releasing, burning, and storing fat. When insulin is high, storage predominates, but turnover continues. When insulin is low, release and oxidation predominate. If you eat fat along with a lot of carbohydrates, it is prone to be stored. When fat is consumed in the context of a well formulated ketogenic diet, it — along with fat released from adipose stores — is prone to be burned. But once digested and absorbed, dietary fat and stored fat enter the ‘turnover pool’ and are in a constant state of mixing.

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22 Comments

  1. Avatar

    Does it make sense then to reduce dietary fat for weight loss as the total amount for the ‘turnover pool’ is reduced and the body will be forced to use stored fat?

    Reply

    1. Virta Health

      If you’re eating fat to satiety, you’ll naturally feel less hungry if you have excess body fat that your body is burning. Check out the chart in this post under mistake #4: https://blog.virtahealth.com/top-keto-mistakes/

      Reply

  2. Avatar

    Is there a rate of oxidation which can be expressed in grams per unit time?

    Reply

    1. Virta Health

      In exercising humans, fat oxidation has been expressed in grams per minute. For example, in the Volek et al. FASTER study, peak fat oxidation in the low carbohydrate groups was reported as (1.54 ± 0.18 vs 0.67 ± 0.14 g/min; P = 0.000) and it occurred at a higher percentage of VO2max (70.3 ± 6.3 vs 54.9 ± 7.8%; P = 0.000).

      Reply

  3. Avatar

    I’m in ketosis on a high fat, moderate protein, low carb meal plan. I’ve always thought ketones happen when your body burns your fat stores. I am curious though, can ketones results from your body burning ingested fat just entering the body, and not touch the fat stores? Thanks!

    Reply

    1. Virta Health

      Great question, Leila! What primarily drives ketone production is the restriction of carbohydrates and, to some extent, protein. Dr. Phinney writes “The liver produces ketones all the time, but the rate of ketogenesis and magnitude of ketosis depends primarily on dietary carbohydrate and protein intake. If you consume enough carbohydrate and protein to elevate the hormone insulin to levels that inhibit fat breakdown (and make glucose the predominant fuel), then ketogenesis operates at idle, translating into blood ketone concentrations about 0.1 mmol/L.” (https://blog.virtahealth.com/what-are-ketones-ketogenesis/)

      Reply

  4. Avatar

    Can you answer Leila’s question more directly please?

    Reply

    1. Virta Health

      What drives ketone production is limiting carbs and protein, not dietary fat intake. If you consume more fat than necessary, then body fat stores will remain unchanged and dietary fat will be used.

      Reply

      1. Avatar

        I don’t think you answered the question. If you are in ketosis (i.e. you are eating low carb), but taking in a lot of fat, would your body turn the fat it takes in before the stored fat?

        Reply

        1. Virta Health

          In the case of MCT oil, your body preferentially has to burn it prior to stored fat. Other fats (long chain triglycerides) are in a constant state of turnover. As Dr. Phinney states above, whether fed or fasted, the body is always releasing, burning, and storing fat.

          Reply

          1. Avatar

            Actually, that seems contradictory to what Dr Phinney said. If you read the literature and what he said when we are in ketosis already. “When fat is consumed in the context of a well formulated ketogenic diet, it — along with fat released from adipose stores — is prone to be burned. But once digested and absorbed, dietary fat and stored fat enter the ‘turnover pool’ and are in a constant state of mixing.” – this means that dietary fat is not burned first, it’s a constant mix. And it doesn’t stop pulling from the cells to allow more dietary fat to enter first into that pool. The body is always burning fat when in ketosis, it doesn’t wait for you to digest and be ready to use the fat you just ate first, the process doesn’t stop and say “oh wait, they just ate fat, we have to digest and use that first to make energy”, it’s way more complex than that. Extra fat that gets converted to energy we don’t need, gets expelled as waste ketones. Until you get to a very LARGE amount of excess dietary fat, well beyond your TDEE. Then it can hinder weight loss. Metabolic damage and hormones play a big part in this as well. MCT oil is a different story as mentioned.

          2. Virta Health

            You are correct. I have gone back to the previous comment and edited it to clarify that specifically MCT are utilized first.

  5. Avatar

    So can i eat 250 grams protein 20 grams carb
    40 grams fat on keto

    I have lots of fat. 35%

    Reply

    1. Avatar

      That’s way too much protein, that your body turns back to sugar, then since it doesn’t need that much sugar for energy it eventually store the excessive protein to fat tissue

      Reply

  6. Avatar

    So what is the amount of “very large” amount of extra dietary fat that has to be ingested to begin storing fat again? It does not make sense that in an environment of low insulin that the body will still continue to burn endogenous fat as well as exogenous fat in excess of body needs and turn into “waste ketones.” Why then does one in deep ketosis eating 200-300 cals in fat above caloric needs gain weight?

    Reply

    1. Virta Health

      Unfortunately, it isn’t as simple as being in ketosis = weight loss, otherwise anyone on a long-term ketogenic diet would waste away. In order to understand the complex dynamics that are happening that lead to weight loss (or gain), I would encourage you to check out this post: https://blog.virtahealth.com/weight-loss-ketogenic-diet/

      Reply

  7. Avatar

    How useful are ketone testing kits if the presence of ketones doesn’t help you differentiate between your body burning stored fat and dietary fat? I’m trying to decide whether it’s worth the investment. Thank you!

    Reply

    1. Virta Health

      Hi Lynn! They are helpful for determining if you are in ketosis and how your body responds to different foods but, you’re right, wouldn’t help you differentiate between stored vs dietary fat burned.

      Reply

  8. Avatar

    In that case, once in ketosis, would it be wise to eventually start to lower dietary fat intake? In order to burn more body fat?

    Reply

    1. Virta Health

      You would run the risk of starvation ketosis versus nutritional ketosis if you were to lower dietary fat. Weight loss is also a complex process where multiple factors are at play. For an in-depth look at ketosis and weight loss, I would encourage you to check out this post: https://blog.virtahealth.com/weight-loss-ketogenic-diet/

      Reply

  9. Avatar

    What exactly is the craze with MCT oils in your morning coffee and adding it to your daily diet plan if your body is going to use it before the turnover pool of fats. I assume our goal is to continually burn the turnover pool to reduce our adipose fat storage ultimately. Why would we want to slow that process down with the addition of MCT’s. Is it like chugging a red bull for your liver?

    Reply

    1. Virta Health

      Hi Eric! Some people use MCT oil in their coffee as a way to extend their fast overnight, others report that it helps with cognition or that it provides them with more energy. It just depends on what your goals are!

      Reply

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