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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37 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. Avatar

      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

    2. Avatar

      Keto24, great questions! I also have wondered the very same thing! Never made sense that the body would burn stored fat when ingesting high fat foods.

      Reply

      1. Virta Health

        Dr. Phinney has previously written: It is possible to eat enough fat when consuming a ketogenic diet to prevent weight (i.e. body fat) loss. But most heavy people find that nutritional ketosis tames their appetite and cravings, such that they tend to eat less than they burn. Even if that deficit starts at just 500 Calories per day, the losses in a year can add up to between 25 and 50 lbs. Eventually, as one’s body fat reserves drop from ‘high’ to ‘normal’, the body senses somewhat greater need and it takes a bit more fat in the diet to achieve the same degree of satiety.

        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

  10. Avatar

    This is what I don’t understand. Why would my body bother to burn stored fat if I’m ingesting fat? Why wouldn’t it just burn the fat I am ingesting for energy? Thereby leaving stored fat on my body which means NO weight loss. At what point does it start to burn stored fat? It seems to me like keto is just a low calorie diet because people eat so much fat that it satiates them. And people have lost weight on low-calorie diets for years. I have googled this topic extensively and very little information is out there on why and how the body starts burning stored fat versus dietary fat on keto.

    Reply

    1. Virta Health

      You may want to read this post as it provides a much more in depth review of weight loss and ketosis and may help answer your questions: https://blog.virtahealth.com/weight-loss-ketogenic-diet/

      Reply

  11. Avatar

    So let’s say I’m already fat. Shouldn’t I eat less fats so that my body burns its fat stores?

    Reply

    1. Virta Health

      Dr. Phinney has previously written: 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.

      Reply

      1. Avatar

        On a no carb diet, will dietary fat always enter the ‘turnover pool’ and be burnt off as fuel? Is the unused fuel disposed of through the urine as ketones? When and why would the body burn off more fuel than it needs, actually waste it?

        Reply

        1. Virta Health

          It isn’t so much a matter of wasting fat but of using it for fuel. The byproduct of fat metabolism is ketone bodies and they can be measured in urine but is not a great indicator of blood ketones. In the case of excess energy intake from fat, it will be stored as fat.

          Reply

  12. Avatar

    Highly interesting article and comments. The concept of a ‘turnover pool’ mentioned, what is it in reality, the physical manifestation?

    Reply

  13. Avatar

    Will dietary fat always enter the ‘turover pool’ first, before being stored or burnt?
    Does fat for storage always come from the ‘turnover pool’?

    Reply

  14. Avatar

    I’ve been doing keto for 5.5 months. When i started i was at 29.1% body fat (per an InBody scan). Now I’m at 18.2% body fat (InBody scan #2).

    When I started I was exercising maybe 20-30 minutes per day. Now I exercise 40-60+ mns per day.

    My question is about hunger: I feel like I’m hungry all the time! I make it to about 3pm on 1,600 calories or so with recommended ratios, but then into the evening 5 days out of the week I have this drive to keep eating. I try to stay with Keto-friendly foods but my calorie count sometimes creeps up towards 2,300 or more.

    I’m drinking adequate water afaik, drinking 2-3 teaspoons of Better than Boullion daily, taking magnesium, using Morton Lite Salt, and drinking electrolytes.

    My sleep has been somewhat erratic — some nights I get 10 hrs (waking up every 2-3 hrs) but some nights it’s 5-6. Could that be the problem?

    Are there any other adjustments I can make to help the hunger impulses calm down? I’m hoping to drop another 5-7 lbs (goal weight!) but it’s proving pretty difficult to get there.

    Any advice would be massively appreciated. Thanks!

    Reply

    1. Avatar

      p.s. I’m female, 47 y.o.

      Reply

    2. Virta Health

      You could be undereating for your body type and that is why you are so hungry. Although you have a goal to lose an additional 5-7 lbs, perhaps that is underweight for you. It is best to listen to your hunger cues while minimizing stress (including poor sleep) and that may include increasing calories.

      Reply

  15. Avatar

    I am wondering the very same thing. I am 240 pounds. I don’t see how eating lots of fat will help me if my body has to burn thru all of that before it burns my body fat. I’m going to start eating 20 grams of carbs protien as suggested in my macros and less fat. I want to burn the fat on my body not the fat I eat.

    Reply

  16. Avatar

    I as well have questioned that Marla. This is how I understand it. Because the need for calories is there and you cant get those calories from carbs, well not over 20 grams, and you cant go too high on the protein as that will kick you out of ketosis, the remaining calories have to come from somewhere, which would be fat. If calories are too low (ie not eating enough fat) you will go into starvation ketosis, not nutritional ketosis. Starvation ketosis is hard to sustain, and hard on your body and can lead to muscle waste. I wouldn’t worry, you will lose just as much weight with eating the additional fat but you wont be miserable, and you wont waste muscle. I started at 360 and I’m down to 300 in 3 months on keto eating the additional fat. Its just being consistent and NO cheat days.

    Reply

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