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    Daily "fat energy" limit

    Posts: 138 Member
    edited November 2024 in Health and Weight Loss
    I am very curious to learn more about the numbers/science on this. Just read in a thread about how our bodies will use muscle and glycogen before burning too much in fat stores. Does anyone have a link?

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    • Posts: 9,170 Member
      You body will only usually metabolise muscle when it has run out of carbs and fat to burn. The idea of starvation mode after eating low calorie for a few days is a diet myth.

    • Posts: 138 Member
      This is exactly what I thought!
      The 'you can only burn so much fat a day' responses in that "800 calories a day" thread definitely sounded woo-ish to me.
    • Posts: 14,464 Member
      I was put on a (medically supervised) VLCD diet to prepare for surgery. The diet was effective and my liver shrank. That would take care of the glycogen stores. So I'd say roughly ten days for glycogen before we run out. I noticed I had to dial back any vigorous exercise. I just didn't have enough "gas in the tank".

      Dr. Google says that keto flu lasts about 3-5 days. But we've all experienced regular fat loss when eating in a deficit.
    • Posts: 908 Member
      Thank you for that, @Tacklewasher.
    • Posts: 7,166 Member
      I find this article really informative about the basics:

      https://www.bodyrecomposition.com/nutrition/nutrient-intake-nutrient-storage-and-nutrient-oxidation.html/
    • Posts: 138 Member
      Very interesting
    • Posts: 21,219 Member
      Nony_Mouse wrote: »
      show previous quotes

      That was me, and no it isn't woo.
      show previous quotes

      I've been attempting to look into this further after seeing a post from someone I trust on these things a couple of days ago that said it's now thought to be much lower, but haven't had any luck finding a source for the lower number. @usmcmp do you have a source for the 4 to 6 cals per lb of body fat you posted about?

      I am away from a computer for a while, but the link to the study was posted in a blog by I believe Alan Aragon.
    • Posts: 5,646 Member
      usmcmp wrote: »
      show previous quotes

      I am away from a computer for a while, but the link to the study was posted in a blog by I believe Alan Aragon.

      Thank you @usmcmp! I shall attempt to find it :)
    • Posts: 138 Member
      I would love to take a look at that too. Post it here if you get s chance, please!
    • Posts: 21,219 Member
      Okay, I dug back through all the articles I had saved and it wasn't in there. I decided to at least dig a big further into the study posted above. There are additional claims that the theoretical biologist who came up with the number adjust it down to 22 calories per pound of body fat. There's nothing published and from what I can tell the guy may have passed away.

      Keep in mind he did not conduct a study, he collected information to create mathematical models to improve data collection and techniques for studies.

      I may be off on what I remember, I've been known to be wrong @Nony_Mouse and it could be double the numbers I stated. I'm still fairly certain it was an article by Alan, but looking at his site I can't find it.
    • Posts: 5,646 Member
      usmcmp wrote: »
      Okay, I dug back through all the articles I had saved and it wasn't in there. I decided to at least dig a big further into the study posted above. There are additional claims that the theoretical biologist who came up with the number adjust it down to 22 calories per pound of body fat. There's nothing published and from what I can tell the guy may have passed away.

      Keep in mind he did not conduct a study, he collected information to create mathematical models to improve data collection and techniques for studies.

      I may be off on what I remember, I've been known to be wrong @Nony_Mouse and it could be double the numbers I stated. I'm still fairly certain it was an article by Alan, but looking at his site I can't find it.

      Thanks muchly anyway @usmcmp :)
    • Posts: 10,968 Member
      Keep in mind the distinction between burning fat vs glycogen while you exercise, and losing fat on a long-term basis, which only requires a calorie deficit no matter what you get your exercise calories from, or even if you don't exercise at all.
    • Posts: 14,261 Member
      usmcmp wrote: »
      Okay, I dug back through all the articles I had saved and it wasn't in there. I decided to at least dig a big further into the study posted above. There are additional claims that the theoretical biologist who came up with the number adjust it down to 22 calories per pound of body fat. There's nothing published and from what I can tell the guy may have passed away.

      Keep in mind he did not conduct a study, he collected information to create mathematical models to improve data collection and techniques for studies.

      I may be off on what I remember, I've been known to be wrong @Nony_Mouse and it could be double the numbers I stated. I'm still fairly certain it was an article by Alan, but looking at his site I can't find it.

      I know that Greg Nuckols wrote an article earlier this year and as mentioned the 22 cal number, though he couldn't find the exact citation. And yes, people need to remember that the 31 calorie figure is the result of studying varies studies and not based in on an experiment showing it to pan out.
    • Posts: 7,122 Member
      NorthCascades wrote: »
      Keep in mind the distinction between burning fat vs glycogen while you exercise, and losing fat on a long-term basis, which only requires a calorie deficit no matter what you get your exercise calories from, or even if you don't exercise at all.

      I think the question is about how much weight can you lose while limiting muscle (LBM) loss. And is a reason why you need to limit your overall loss rate. Going beyond that and you will lose more LBM.

      But that's only my take on it and I could easily be wrong.
    • Posts: 11,068 Member
      Tacklewasher wrote: »
      show previous quotes

      I think the question is about how much weight can you lose while limiting muscle (LBM) loss. And is a reason why you need to limit your overall loss rate. Going beyond that and you will lose more LBM.

      But that's only my take on it and I could easily be wrong.

      Another thing to consider is that that paper is attempting to establish a limit on rate of fat oxidation. In theory, going well over this limit would increase losses of fat free mass, but staying under this limit does not guarantee or even imply that all losses will come from fat.
    • Posts: 138 Member
      Tacklewasher wrote: »
      show previous quotes

      I think the question is about how much weight can you lose while limiting muscle (LBM) loss. And is a reason why you need to limit your overall loss rate. Going beyond that and you will lose more LBM.

      But that's only my take on it and I could easily be wrong.

      My confusion is less about long term fat loss or even minimizing muscle loss. It's more about the concept of a daily limit. I'm imagining reaching my "daily limit" of fat usage after using up all the glycogen and then just.. *clunk* ..dead. Because how can a heart keep beating without energy to use?

    • Posts: 7,722 Member
      edited September 2017
      ColetteM6 wrote: »
      show previous quotes

      My confusion is less about long term fat loss or even minimizing muscle loss. It's more about the concept of a daily limit. I'm imagining reaching my "daily limit" of fat usage after using up all the glycogen and then just.. *clunk* ..dead. Because how can a heart keep beating without energy to use?

      You'd pull the energy you needed from other tissues after you'd utilized the maximum energy you could from fat stores.

      Now, IIRC, you're going to be doing some of that anyway. The key is to minimize it by not going over what you can tap into fat stores for the day and making it absolutely necessary to draw from muscles.



    • Posts: 7,122 Member
      SideSteel wrote: »
      show previous quotes

      Another thing to consider is that that paper is attempting to establish a limit on rate of fat oxidation. In theory, going well over this limit would increase losses of fat free mass, but staying under this limit does not guarantee or even imply that all losses will come from fat.

      Understood. It's why we try to keep protein well above the minimum RDA levels and exercise. At least we can do our best to limit the non-fat loss.
    • Posts: 1,232 Member
      Pretty much the only evidence you need that "starvation mode" is nonsense is to talk to anybody who's had gastric bypass or some other similar surgery. They go on medically supervised diets with crazy low calories and drop weight at rates that would make your head spin. But EVERYTHING is tightly controlled, and they undergo routine medical examinations and blood tests to calibrate what they eat and what they supplement. Just cutting your food to 800 calories a day without that would probably end in disaster.
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