Daily "fat energy" limit

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ColetteM6
ColetteM6 Posts: 138 Member
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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  • tinkerbellang83
    tinkerbellang83 Posts: 9,136 Member
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    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.

  • ColetteM6
    ColetteM6 Posts: 138 Member
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    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.
  • jgnatca
    jgnatca Posts: 14,464 Member
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    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.
  • Heather4448
    Heather4448 Posts: 908 Member
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    Thank you for that, @Tacklewasher.
  • BusyRaeNOTBusty
    BusyRaeNOTBusty Posts: 7,166 Member
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    I find this article really informative about the basics:

    https://www.bodyrecomposition.com/nutrition/nutrient-intake-nutrient-storage-and-nutrient-oxidation.html/
  • ColetteM6
    ColetteM6 Posts: 138 Member
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    Very interesting
  • usmcmp
    usmcmp Posts: 21,220 Member
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    Nony_Mouse wrote: »
    ColetteM6 wrote: »
    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.

    That was me, and no it isn't woo.
    Tacklewasher wrote: »
    Here is the link to the abstract on the research paper.

    https://www.ncbi.nlm.nih.gov/pubmed/15615615

    Works out to ~31 Cal per lb of body fat per day.

    I'm about 65 lbs of body fat, so my max per day is 2,015, or a bit over 1/2 lb per day. Now that's not going to happen as I'm not prepared to eat that little, but there is a limit to how much fat can be burned in a day.

    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.
  • Nony_Mouse
    Nony_Mouse Posts: 5,646 Member
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    usmcmp wrote: »
    Nony_Mouse wrote: »
    ColetteM6 wrote: »
    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.

    That was me, and no it isn't woo.
    Tacklewasher wrote: »
    Here is the link to the abstract on the research paper.

    https://www.ncbi.nlm.nih.gov/pubmed/15615615

    Works out to ~31 Cal per lb of body fat per day.

    I'm about 65 lbs of body fat, so my max per day is 2,015, or a bit over 1/2 lb per day. Now that's not going to happen as I'm not prepared to eat that little, but there is a limit to how much fat can be burned in a day.

    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.

    Thank you @usmcmp! I shall attempt to find it :)
  • ColetteM6
    ColetteM6 Posts: 138 Member
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    I would love to take a look at that too. Post it here if you get s chance, please!
  • usmcmp
    usmcmp Posts: 21,220 Member
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    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.
  • Nony_Mouse
    Nony_Mouse Posts: 5,646 Member
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    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 :)
  • NorthCascades
    NorthCascades Posts: 10,970 Member
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    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.
  • jemhh
    jemhh Posts: 14,261 Member
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    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.
  • Tacklewasher
    Tacklewasher Posts: 7,122 Member
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    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.
  • SideSteel
    SideSteel Posts: 11,068 Member
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    Tacklewasher wrote: »
    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.

    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.
  • ColetteM6
    ColetteM6 Posts: 138 Member
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    Tacklewasher wrote: »
    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.

    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?

  • GottaBurnEmAll
    GottaBurnEmAll Posts: 7,722 Member
    edited September 2017
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    ColetteM6 wrote: »
    Tacklewasher wrote: »
    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.

    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.



  • Tacklewasher
    Tacklewasher Posts: 7,122 Member
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    SideSteel wrote: »
    Tacklewasher wrote: »
    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.

    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.

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