Limit to the amount of fat that can be burned in a day?

try2again
try2again Posts: 3,562 Member
edited November 15 in Health and Weight Loss
I've often seen it said in the forums, and have repeated it myself, that there is a limit to the amount of fat that a person's body can burn in a day, and that when a person has too great of a deficit, the body will then burn more lean muscle mass to compensate. Recently I saw this questioned on a thread and realized I don't know the basis for this statement myself. When I googled the topic, most of the sources didn't seem particularly reliable (mostly just threads on other forums). Can anyone share credible links or info on the topic? Also, is this where the recommendation comes from of a reasonable weekly weight loss goal of 1% of body weight? Thanks :)

Replies

  • Chadxx
    Chadxx Posts: 1,199 Member
    IIRC, I believe it is supposed to be 31 calories per pound of body fat.
  • kimny72
    kimny72 Posts: 16,011 Member
    try2again wrote: »
    I've often seen it said in the forums, and have repeated it myself, that there is a limit to the amount of fat that a person's body can burn in a day, and that when a person has too great of a deficit, the body will then burn more lean muscle mass to compensate. Recently I saw this questioned on a thread and realized I don't know the basis for this statement myself. When I googled the topic, most of the sources didn't seem particularly reliable (mostly just threads on other forums). Can anyone share credible links or info on the topic? Also, is this where the recommendation comes from of a reasonable weekly weight loss goal of 1% of body weight? Thanks :)

    Like you, I have only ever heard that here, and since it is often stated by posters who usually have their facts straight, and it makes sense to me, I go with it :)

    I have always assumed the 1% of body weight figure was tied to this idea.

    I hope you get some informative responses!
  • lemurcat12
    lemurcat12 Posts: 30,886 Member
    The source, I believe, is Lyle McDonald, who credits the information to his reading of this paper: https://www.ncbi.nlm.nih.gov/pubmed/15615615

    I have not read the paper. McDonald is a decent source in general, but I don't know how he evaluated the paper, if there is contrary info, etc.
  • try2again
    try2again Posts: 3,562 Member
    kimny72 wrote: »
    try2again wrote: »
    I've often seen it said in the forums, and have repeated it myself, that there is a limit to the amount of fat that a person's body can burn in a day, and that when a person has too great of a deficit, the body will then burn more lean muscle mass to compensate. Recently I saw this questioned on a thread and realized I don't know the basis for this statement myself. When I googled the topic, most of the sources didn't seem particularly reliable (mostly just threads on other forums). Can anyone share credible links or info on the topic? Also, is this where the recommendation comes from of a reasonable weekly weight loss goal of 1% of body weight? Thanks :)

    Like you, I have only ever heard that here, and since it is often stated by posters who usually have their facts straight, and it makes sense to me, I go with it :)

    I have always assumed the 1% of body weight figure was tied to this idea.

    I hope you get some informative responses!

    Same here- it's not that I doubt it, I'd just like to be able to back it up. :)
  • TR0berts
    TR0berts Posts: 7,739 Member
    edited January 2017
    lemurcat12 wrote: »
    The source, I believe, is Lyle McDonald, who credits the information to his reading of this paper: https://www.ncbi.nlm.nih.gov/pubmed/15615615

    I have not read the paper. McDonald is a decent source in general, but I don't know how he evaluated the paper, if there is contrary info, etc.
    I just found that from Lyle's forum.

    Per the paper:
    (290+/-25) kJ/kgd

    I don't know what kgd is, but kJ ~ 60 Cals. eta: If kgd simply means kg of fat, then it's about 27 Cal/lb.

  • lemurcat12
    lemurcat12 Posts: 30,886 Member
    31 calories/lb of fat is generally higher than the 1-2 lbs per week or 1% per week, I think.

    Let's say that at 125 I have about 30 lb of fat and was 24% BF. That would mean I could have a deficit of 930, or about 1.86 lb/week -- within the 1-2 lb zone, but well over 1%.

    That would be a crazy deficit given sedentary TDEE at that size (5'3), but the bigger issue is that it's not uncommon for people to have like 100 lb of BF when they have a lot to lose, or even more. If I were 210 and 50% BF, could I really have a deficit of over 3000 calories per day? No, because my TDEE wouldn't be close to that high.

    It does explain how people on Biggest Loser can lose so much, but I'll stick with the 1% figure and a general sense of what is necessary for a balanced, satisfying diet when at a deficit.
  • TR0berts
    TR0berts Posts: 7,739 Member
    edited January 2017
    In addition, Greg Nuckols touches on this on a recent article on strengththeory in the "How fast can I lose fat?" section.
    A 2005 study found that body fat stores can liberate, at most, about 31kcal/day to be burned. In a subsequent interview (which, unfortunately, I can’t find the link to anymore), the lead researcher admitted he botched a couple of calculations, and the limit was closer to 22kcal/day from each pound of body fat.

    He then goes on to say that it's not particularly realistic to expect that much. I would agree - at 182 lb and probably about 17% bf, that puts me at approximately a 1.5 lb per week deficit that would be doable. I doubt that would be good.
  • try2again
    try2again Posts: 3,562 Member
    lemurcat12 wrote: »
    The source, I believe, is Lyle McDonald, who credits the information to his reading of this paper: https://www.ncbi.nlm.nih.gov/pubmed/15615615

    I have not read the paper. McDonald is a decent source in general, but I don't know how he evaluated the paper, if there is contrary info, etc.

    Thank you... I read the link and some articles by McDonald (though much was over my head). I thought it was interesting that even he didn't know where the original idea of a 2 lb/week limit originated. Makes me wonder how so many are aware of this, when so little has apparently been written on it?
  • Gallowmere1984
    Gallowmere1984 Posts: 6,626 Member
    try2again wrote: »
    lemurcat12 wrote: »
    The source, I believe, is Lyle McDonald, who credits the information to his reading of this paper: https://www.ncbi.nlm.nih.gov/pubmed/15615615

    I have not read the paper. McDonald is a decent source in general, but I don't know how he evaluated the paper, if there is contrary info, etc.

    Thank you... I read the link and some articles by McDonald (though much was over my head). I thought it was interesting that even he didn't know where the original idea of a 2 lb/week limit originated. Makes me wonder how so many are aware of this, when so little has apparently been written on it?

    I can only assume that it's just born of the "slower is better" nonsense that seems to plague most private human pursuits. Anyone who believes that's the upper "safe" limit for everyone is goofy. I can (and have) peeled 1.5-2lbs. of fat off per week while weighing in the 160-170s and 15-18% bf range, without appreciable LBM loss. If that same "limit" applies to a guy at 250 and 35%, I'll kiss your *kitten*.
  • Gallowmere1984
    Gallowmere1984 Posts: 6,626 Member
    try2again wrote: »
    Gallowmere1984 wrote: »
    try2again wrote: »
    lemurcat12 wrote: »
    The source, I believe, is Lyle McDonald, who credits the information to his reading of this paper: https://www.ncbi.nlm.nih.gov/pubmed/15615615

    I have not read the paper. McDonald is a decent source in general, but I don't know how he evaluated the paper, if there is contrary info, etc.

    Thank you... I read the link and some articles by McDonald (though much was over my head). I thought it was interesting that even he didn't know where the original idea of a 2 lb/week limit originated. Makes me wonder how so many are aware of this, when so little has apparently been written on it?

    I can only assume that it's just born of the "slower is better" nonsense that seems to plague most private human pursuits. Anyone who believes that's the upper "safe" limit for everyone is goofy. I can (and have) peeled 1.5-2lbs. of fat off per week while weighing in the 160-170s and 15-18% bf range, without appreciable LBM loss. If that same "limit" applies to a guy at 250 and 35%, I'll kiss your *kitten*.
    Gallowmere1984 wrote: »
    try2again wrote: »
    lemurcat12 wrote: »
    The source, I believe, is Lyle McDonald, who credits the information to his reading of this paper: https://www.ncbi.nlm.nih.gov/pubmed/15615615

    I have not read the paper. McDonald is a decent source in general, but I don't know how he evaluated the paper, if there is contrary info, etc.

    Thank you... I read the link and some articles by McDonald (though much was over my head). I thought it was interesting that even he didn't know where the original idea of a 2 lb/week limit originated. Makes me wonder how so many are aware of this, when so little has apparently been written on it?

    I can only assume that it's just born of the "slower is better" nonsense that seems to plague most private human pursuits. Anyone who believes that's the upper "safe" limit for everyone is goofy. I can (and have) peeled 1.5-2lbs. of fat off per week while weighing in the 160-170s and 15-18% bf range, without appreciable LBM loss. If that same "limit" applies to a guy at 250 and 35%, I'll kiss your *kitten*.

    I know experienced bodybuilders feel comfortable manipulating their body fat in relatively extreme ways, but I don't think it's particularly wise to encourage the average person to overly restrict their calories in an effort to make the process go faster. People put enough pressure on themselves as it is. 1% of body weight seems fine.

    Oh, I do not encourage such, nor do I believe anyone should. This whole thread seemed more along the lines of "what is or isn't possible" than what a good recommendation for the masses would be.
  • try2again
    try2again Posts: 3,562 Member
    edited January 2017
    Gallowmere1984 wrote: »
    try2again wrote: »
    Gallowmere1984 wrote: »
    try2again wrote: »
    lemurcat12 wrote: »
    The source, I believe, is Lyle McDonald, who credits the information to his reading of this paper: https://www.ncbi.nlm.nih.gov/pubmed/15615615

    I have not read the paper. McDonald is a decent source in general, but I don't know how he evaluated the paper, if there is contrary info, etc.

    Thank you... I read the link and some articles by McDonald (though much was over my head). I thought it was interesting that even he didn't know where the original idea of a 2 lb/week limit originated. Makes me wonder how so many are aware of this, when so little has apparently been written on it?

    I can only assume that it's just born of the "slower is better" nonsense that seems to plague most private human pursuits. Anyone who believes that's the upper "safe" limit for everyone is goofy. I can (and have) peeled 1.5-2lbs. of fat off per week while weighing in the 160-170s and 15-18% bf range, without appreciable LBM loss. If that same "limit" applies to a guy at 250 and 35%, I'll kiss your *kitten*.
    Gallowmere1984 wrote: »
    try2again wrote: »
    lemurcat12 wrote: »
    The source, I believe, is Lyle McDonald, who credits the information to his reading of this paper: https://www.ncbi.nlm.nih.gov/pubmed/15615615

    I have not read the paper. McDonald is a decent source in general, but I don't know how he evaluated the paper, if there is contrary info, etc.

    Thank you... I read the link and some articles by McDonald (though much was over my head). I thought it was interesting that even he didn't know where the original idea of a 2 lb/week limit originated. Makes me wonder how so many are aware of this, when so little has apparently been written on it?

    I can only assume that it's just born of the "slower is better" nonsense that seems to plague most private human pursuits. Anyone who believes that's the upper "safe" limit for everyone is goofy. I can (and have) peeled 1.5-2lbs. of fat off per week while weighing in the 160-170s and 15-18% bf range, without appreciable LBM loss. If that same "limit" applies to a guy at 250 and 35%, I'll kiss your *kitten*.

    I know experienced bodybuilders feel comfortable manipulating their body fat in relatively extreme ways, but I don't think it's particularly wise to encourage the average person to overly restrict their calories in an effort to make the process go faster. People put enough pressure on themselves as it is. 1% of body weight seems fine.

    Oh, I do not encourage such, nor do I believe anyone should. This whole thread seemed more along the lines of "what is or isn't possible" than what a good recommendation for the masses would be.

    I didn't really think you were. I could just see a newbie reading that and feeling like they could "go for it". Should have worded my response differently. I do happen to think "slower is better" in that it enables a person to introduce new habits gradually and get comfortable with them, as opposed to a sudden massive loss and then going into maintenance "cold". But I know the statistics on long-term maintenance don't show an advantage long-term.

    Yeah, I was mostly interested in the factual basis for that statement about only being able to burn so much fat before your body starts cannibalizing a higher proportion muscle. I'm surprised there isn't more info out there, outside of the bodybuilding world.
  • TimothyFish
    TimothyFish Posts: 4,925 Member
    try2again wrote: »
    Gallowmere1984 wrote: »
    try2again wrote: »
    Gallowmere1984 wrote: »
    try2again wrote: »
    lemurcat12 wrote: »
    The source, I believe, is Lyle McDonald, who credits the information to his reading of this paper: https://www.ncbi.nlm.nih.gov/pubmed/15615615

    I have not read the paper. McDonald is a decent source in general, but I don't know how he evaluated the paper, if there is contrary info, etc.

    Thank you... I read the link and some articles by McDonald (though much was over my head). I thought it was interesting that even he didn't know where the original idea of a 2 lb/week limit originated. Makes me wonder how so many are aware of this, when so little has apparently been written on it?

    I can only assume that it's just born of the "slower is better" nonsense that seems to plague most private human pursuits. Anyone who believes that's the upper "safe" limit for everyone is goofy. I can (and have) peeled 1.5-2lbs. of fat off per week while weighing in the 160-170s and 15-18% bf range, without appreciable LBM loss. If that same "limit" applies to a guy at 250 and 35%, I'll kiss your *kitten*.
    Gallowmere1984 wrote: »
    try2again wrote: »
    lemurcat12 wrote: »
    The source, I believe, is Lyle McDonald, who credits the information to his reading of this paper: https://www.ncbi.nlm.nih.gov/pubmed/15615615

    I have not read the paper. McDonald is a decent source in general, but I don't know how he evaluated the paper, if there is contrary info, etc.

    Thank you... I read the link and some articles by McDonald (though much was over my head). I thought it was interesting that even he didn't know where the original idea of a 2 lb/week limit originated. Makes me wonder how so many are aware of this, when so little has apparently been written on it?

    I can only assume that it's just born of the "slower is better" nonsense that seems to plague most private human pursuits. Anyone who believes that's the upper "safe" limit for everyone is goofy. I can (and have) peeled 1.5-2lbs. of fat off per week while weighing in the 160-170s and 15-18% bf range, without appreciable LBM loss. If that same "limit" applies to a guy at 250 and 35%, I'll kiss your *kitten*.

    I know experienced bodybuilders feel comfortable manipulating their body fat in relatively extreme ways, but I don't think it's particularly wise to encourage the average person to overly restrict their calories in an effort to make the process go faster. People put enough pressure on themselves as it is. 1% of body weight seems fine.

    Oh, I do not encourage such, nor do I believe anyone should. This whole thread seemed more along the lines of "what is or isn't possible" than what a good recommendation for the masses would be.

    I didn't really think you were. I could just see a newbie reading that and feeling like they could "go for it". Should have worded my response differently. I do happen to think "slower is better" in that it enables a person to introduce new habits gradually and get comfortable with them, as opposed to a sudden massive loss and then going into maintenance "cold". But I know the statistics on long-term maintenance don't show an advantage long-term.

    Yeah, I was mostly interested in the factual basis for that statement about only being able to burn so much fat before your body starts cannibalizing a higher proportion muscle. I'm surprised there isn't more info out there, outside of the bodybuilding world.

    That's probably because the whole point of body building is to cut the fat to show off big muscles. Other disciplines are more concerned about the performance of the muscles. While they give thought to how slowly fat is able to release energy, they counter that by supplementing it with energy from other sources--usually in the form of carbs eaten before and during exercise. The limit of their thought of cannibalism is to counteract it by eating protein during recovery. Also, even is some cannibalism takes place it isn't a big concern because weight is the primary concern. If the decrease in weight makes up for a small decrease in muscle then all is good.
  • Jruzer
    Jruzer Posts: 3,501 Member
    edited January 2017
    TR0berts wrote: »
    lemurcat12 wrote: »
    The source, I believe, is Lyle McDonald, who credits the information to his reading of this paper: https://www.ncbi.nlm.nih.gov/pubmed/15615615

    I have not read the paper. McDonald is a decent source in general, but I don't know how he evaluated the paper, if there is contrary info, etc.
    I just found that from Lyle's forum.

    Per the paper:
    (290+/-25) kJ/kgd

    I don't know what kgd is, but kJ ~ 60 Cals. eta: If kgd simply means kg of fat, then it's about 27 Cal/lb.

    290 kJ/kg-d is 290 kJ per kilogram per day. Alternately [kJ][kg]^-1[d]^-1, or kJ/kg/d, but this last one is ambiguous.

    We're so used to including "days" in our discussions here ("Anyone else on 1200?") that we sometimes forget that it should be explicitly called out.
  • TR0berts
    TR0berts Posts: 7,739 Member
    Jruzer wrote: »
    TR0berts wrote: »
    lemurcat12 wrote: »
    The source, I believe, is Lyle McDonald, who credits the information to his reading of this paper: https://www.ncbi.nlm.nih.gov/pubmed/15615615

    I have not read the paper. McDonald is a decent source in general, but I don't know how he evaluated the paper, if there is contrary info, etc.
    I just found that from Lyle's forum.

    Per the paper:
    (290+/-25) kJ/kgd

    I don't know what kgd is, but kJ ~ 60 Cals. eta: If kgd simply means kg of fat, then it's about 27 Cal/lb.

    290 kJ/kg-d is 290 kJ per kilogram per day. Alternately [kJ][kg]^-1[d]^-1, or kJ/kg/d, but this last one is ambiguous.

    We're so used to including "days" in our discussions here ("Anyone else on 1200?") that we sometimes forget that it should be explicitly called out.

    Ah, OK. I'd probably write it as kJ/(kg/d), but that would probably confuse others. I'm not sure I'd have come up with that, since day isn't a standard unit. But, it makes sense.
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