What role does metabolism actually play in weight loss?

OneHundredToLose
OneHundredToLose Posts: 8,523 Member
edited November 2024 in Health and Weight Loss
So, since coming to MFP, I've had to re-learn a lot of what I thought I knew about weight loss and dieting in general. It's now become apparent to me that calories are king, so to speak. What you eat doesn't matter as much as how much you eat. I've been losing weight at my charted rate eating pretty much whatever I feel like eating, as long as I control my portions and stay under my calorie goal.

However, I still hear a lot of talk on both sides about metabolism, and what effect a fast / high metabolism can have on weight loss. What are the actual facts? I'm not interested in opinions as much as real, proven facts. I've done research into this myself, but what I've found is not conclusive either way.
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Replies

  • Schtroumpfkin
    Schtroumpfkin Posts: 123 Member
    Hi OneHundred... I can't answer this - I'm not remotely qualified. But, in terms of "what are the actual facts", my opinion is that we do have to live with the answer that "nobody really knows". Even scientific studies can be accused of bias (either due to who they are funded by, what product they are pedaling or even because the scientist wants to "cause a stir"). Less cynically, there are often genuine problems with the ways studies are conducted - things that nobody meant to do wrong - but it was something they just hadn't considered. There is also potentially something called "publication bias" (lookup the TED talk) and many, many other factors. You are always going to get differences of opinion (and data!)

    However, you sound like you enjoy your research. I recently read a book called "Body by Science" by Doug McDuff and John Little, which was a satisfying and compelling read. It tells you the ways that the body's cells actually convert various macronutrients into energy that the body can use (which I guess is what you refer to by "metabolism"). It was easy to understand (relatively...a few bits lost me a touch) and enjoyable.

    Don't worry, I have no links to this book or its authors. I just read it in my garden over the past few weekends and it just seemed very credible and if nothing else, I feel more informed about the science around how my body uses food. Albeit I am a strong advocate of the straightforward "calories in, calories out" formula (sometimes, simple is best) - this book does go some way to explain the differences between food groups and how the body interacts with them. I have subsequently decided to base some of my approach based on what was in this book. Let me know how you get on.

    All the best!
  • LKArgh
    LKArgh Posts: 5,178 Member
    http://www.mayoclinic.org/healthy-lifestyle/weight-loss/in-depth/metabolism/art-20046508

    Metabolism is the process by which your body converts what you eat and drink into energy. During this complex biochemical process, calories in food and beverages are combined with oxygen to release the energy your body needs to function.

    In brief, metabolism plays a role in keeping you alive.
  • OneHundredToLose
    OneHundredToLose Posts: 8,523 Member
    aggelikik wrote: »
    http://www.mayoclinic.org/healthy-lifestyle/weight-loss/in-depth/metabolism/art-20046508

    Metabolism is the process by which your body converts what you eat and drink into energy. During this complex biochemical process, calories in food and beverages are combined with oxygen to release the energy your body needs to function.

    In brief, metabolism plays a role in keeping you alive.

    Right, but I guess what I am trying to ask is does having a faster / slower metabolism actually affect weight loss, as many claim?
  • KittensMaster
    KittensMaster Posts: 748 Member
    I see this at the gym

    Some people are hard gainers. They drink the calorie heavy shakes, eat insane amounts, lift hard....

    And barely gain muscle

    They eat like mad and stay lean

    Others like me, eat much less, gain muscle pretty easily, but struggle getting lean. I never drink the Gainer Protein shakes, always eat less than those guys.

    And I do lots of cardio to keep the weight controlled and count calories

    It does seem to be that way. Some have a different motor than others.

    It really does not matter. You have to adapt to what you have and deal.

  • strong_curves
    strong_curves Posts: 2,229 Member
    aggelikik wrote: »
    http://www.mayoclinic.org/healthy-lifestyle/weight-loss/in-depth/metabolism/art-20046508

    Metabolism is the process by which your body converts what you eat and drink into energy. During this complex biochemical process, calories in food and beverages are combined with oxygen to release the energy your body needs to function.

    In brief, metabolism plays a role in keeping you alive.

    Right, but I guess what I am trying to ask is does having a faster / slower metabolism actually affect weight loss, as many claim?

    In the context that you're talking about, which I think is (and correct me if i'm wrong), you see a person who's slim and you notice they tend to eat a lot all the time so you assume they have a faster metabolism. Or you see some who is heavy and they claim they don't eat a lot they're heavy because they have a "slow metabolism". That particular idea of fast/slow metabolism is a myth.
  • OneHundredToLose
    OneHundredToLose Posts: 8,523 Member
    aggelikik wrote: »
    http://www.mayoclinic.org/healthy-lifestyle/weight-loss/in-depth/metabolism/art-20046508

    Metabolism is the process by which your body converts what you eat and drink into energy. During this complex biochemical process, calories in food and beverages are combined with oxygen to release the energy your body needs to function.

    In brief, metabolism plays a role in keeping you alive.

    Right, but I guess what I am trying to ask is does having a faster / slower metabolism actually affect weight loss, as many claim?

    In the context that you're talking about, which I think is (and correct me if i'm wrong), you see a person who's slim and you notice they tend to eat a lot all the time so you assume they have a faster metabolism. Or you see some who is heavy and they claim they don't eat a lot they're heavy because they have a "slow metabolism". That particular idea of fast/slow metabolism is a myth.

    That's kind of what I figured. It's common to hear people say that they "just have a fast metabolism", but what I've experienced so far seems to indicate that it doesn't matter. I guess I can gather, then, that metabolism-boosting supplements are worthless for weight loss?
  • bendyourkneekatie
    bendyourkneekatie Posts: 696 Member
    I think there's two things: for the most part it's a myth, and then in the rare instances it exists (certain medical conditions) it generally accounts for a fairly small difference in weight. And similarly, there may be some foods/supplements that burn some calories, but the amount is tiny in comparison to the deficit required for weight loss.
  • strong_curves
    strong_curves Posts: 2,229 Member
    aggelikik wrote: »
    http://www.mayoclinic.org/healthy-lifestyle/weight-loss/in-depth/metabolism/art-20046508

    Metabolism is the process by which your body converts what you eat and drink into energy. During this complex biochemical process, calories in food and beverages are combined with oxygen to release the energy your body needs to function.

    In brief, metabolism plays a role in keeping you alive.

    Right, but I guess what I am trying to ask is does having a faster / slower metabolism actually affect weight loss, as many claim?

    In the context that you're talking about, which I think is (and correct me if i'm wrong), you see a person who's slim and you notice they tend to eat a lot all the time so you assume they have a faster metabolism. Or you see some who is heavy and they claim they don't eat a lot they're heavy because they have a "slow metabolism". That particular idea of fast/slow metabolism is a myth.

    That's kind of what I figured. It's common to hear people say that they "just have a fast metabolism", but what I've experienced so far seems to indicate that it doesn't matter. I guess I can gather, then, that metabolism-boosting supplements are worthless for weight loss?


    Yeah, save your $$$. For weight loss, it's really just calories in vs calories out. Eating less than you burn.



  • suziecue20
    suziecue20 Posts: 567 Member
    I have only ever met one person who I could say might have 'a very fast metabolism' and is 'pencil thin' and eats loads and drinks vast amounts of alcohol. During a normal day this person is never still, always on the move and walks at a fast pace. However, I wonder is it a fast metabolism or does alcoholism have something to do with it?
  • LKArgh
    LKArgh Posts: 5,178 Member
    aggelikik wrote: »
    http://www.mayoclinic.org/healthy-lifestyle/weight-loss/in-depth/metabolism/art-20046508

    Metabolism is the process by which your body converts what you eat and drink into energy. During this complex biochemical process, calories in food and beverages are combined with oxygen to release the energy your body needs to function.

    In brief, metabolism plays a role in keeping you alive.

    Right, but I guess what I am trying to ask is does having a faster / slower metabolism actually affect weight loss, as many claim?

    There is no such thing for healthy individuals. There are a few medical problems that affect metabolism, and if you have reason to suspect thsi is your case, you need to see a dr.
  • LKArgh
    LKArgh Posts: 5,178 Member
    aggelikik wrote: »
    http://www.mayoclinic.org/healthy-lifestyle/weight-loss/in-depth/metabolism/art-20046508

    Metabolism is the process by which your body converts what you eat and drink into energy. During this complex biochemical process, calories in food and beverages are combined with oxygen to release the energy your body needs to function.

    In brief, metabolism plays a role in keeping you alive.

    Right, but I guess what I am trying to ask is does having a faster / slower metabolism actually affect weight loss, as many claim?

    In the context that you're talking about, which I think is (and correct me if i'm wrong), you see a person who's slim and you notice they tend to eat a lot all the time so you assume they have a faster metabolism. Or you see some who is heavy and they claim they don't eat a lot they're heavy because they have a "slow metabolism". That particular idea of fast/slow metabolism is a myth.

    That's kind of what I figured. It's common to hear people say that they "just have a fast metabolism", but what I've experienced so far seems to indicate that it doesn't matter. I guess I can gather, then, that metabolism-boosting supplements are worthless for weight loss?

    There are meds that will "boost" your metabolism, as in will pretty much make you ill. Obviously the use of such meds for weight loss is both very dangerous and not legal.
  • OneHundredToLose
    OneHundredToLose Posts: 8,523 Member
    aggelikik wrote: »
    aggelikik wrote: »
    http://www.mayoclinic.org/healthy-lifestyle/weight-loss/in-depth/metabolism/art-20046508

    Metabolism is the process by which your body converts what you eat and drink into energy. During this complex biochemical process, calories in food and beverages are combined with oxygen to release the energy your body needs to function.

    In brief, metabolism plays a role in keeping you alive.

    Right, but I guess what I am trying to ask is does having a faster / slower metabolism actually affect weight loss, as many claim?

    There is no such thing for healthy individuals. There are a few medical problems that affect metabolism, and if you have reason to suspect thsi is your case, you need to see a dr.

    I definitely don't think it's the case for me, which is why it's so surprising for me to learn that it's most likely not the case for 99% of people. We're kind of told all our lives that it's a big deal, and you just either have it or you don't, but I'm now finding that it's bunk.
  • strong_curves
    strong_curves Posts: 2,229 Member
    aggelikik wrote: »
    aggelikik wrote: »
    http://www.mayoclinic.org/healthy-lifestyle/weight-loss/in-depth/metabolism/art-20046508

    Metabolism is the process by which your body converts what you eat and drink into energy. During this complex biochemical process, calories in food and beverages are combined with oxygen to release the energy your body needs to function.

    In brief, metabolism plays a role in keeping you alive.

    Right, but I guess what I am trying to ask is does having a faster / slower metabolism actually affect weight loss, as many claim?

    There is no such thing for healthy individuals. There are a few medical problems that affect metabolism, and if you have reason to suspect thsi is your case, you need to see a dr.

    I definitely don't think it's the case for me, which is why it's so surprising for me to learn that it's most likely not the case for 99% of people. We're kind of told all our lives that it's a big deal, and you just either have it or you don't, but I'm now finding that it's bunk.

    There's a ton of stuff we've been told all our lives about weight loss that's just WRONG! LOL Being on mfp has been an eye opener when it comes to weight loss for me.

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  • Qskim
    Qskim Posts: 1,145 Member
    While I don't exactly know what role metabolism plays in weight loss, I feel confident in saying:
    Not as much of a role as many would think.
    In other words, not as much of a role as some would want there to be.

    Agree.
  • DeguelloTex
    DeguelloTex Posts: 6,652 Member
    Like most things, the overwhelming majority of metabolisms fall into a relatively narrow range. Like most things, there are outliers with significantly faster or slower metabolisms. Like most things, chances are that you (generic "you") aren't one of those outliers. Even if you are, you can still lose weight once you identity your maintenance level, even if that level is lower than predicted.
  • honkytonks85
    honkytonks85 Posts: 669 Member
    Metabolism encompasses all the processes in your body that make it function (including digestion). For the purposes of this post I will focus specifically on your metabolic rate (also known as your BMR).

    Some people burn more calories than others, this is your metabolism. Men typically burn more because they are leaner and taller. Basically lean & tall = faster metabolism = you can eat more food. Short with low lean body mass (eg more fat than muscle) = slower metabolism = you have to eat less. The number of calories you burn in a day varies by several hundred or more from person to person. Also as you get older you burn fewer calories. If you have a faster metabolism you will also burn more during physical activity. Sadly the reality is those who are shorter and who are less lean simply have to adjust their eating down.

    For those who say metabolism plays no part, you are wrong, it absolutely plays every part of the weight loss process, it is literally the reason you gain or lose weight.
  • DeguelloTex
    DeguelloTex Posts: 6,652 Member
    edited September 2015
    No, the literal reason you gain or lose weight is eating more than your TDEE.

    Most people don't equate TDEE with non-exercise metabolism when discussing slow or fast metabolisms.
  • lindsey1979
    lindsey1979 Posts: 2,395 Member
    I think a lot of this comes down to genetics and medical issues (if any are present). The classic ectomoph, mesomorph and endomorph people. As strong_curves talked about, there certainly are people that have a MUCH easier time maintaining a healthy weight (naturally thin folks) and those that have MUCH easier time building muscle (usually also gaining fat). It's a spectrum. On the extremes you see the elite athletes -- whether it's a marathon runner on one side or powerlifters on the other. They no doubt are genetic freaks -- just like any elite athlete. That's not to say they don't work hard -- of course, they do -- but they have certain genetics that allow them to reach that level. Not everyone could work as hard and get those same results -- it's just not how the world works.

    So, it's all about being the best YOU. Being the best version of your genetic potential. So you may struggle more with weight loss/management or you may struggle more with gaining weight/muscle. Depending on your issues, certain strategies may work better or worse for you --- whether that's adjusting macros (carbs especially), using an intermittent fasting regime like 16:8 or 5:2, calorie cycling, etc. Deficits work for those without medical issues, but how you create that deficit may yield dramatically different results depending on your individual circumstances. A lot of it is trial and error figuring out what works best for you. But, yes, there are undoubtedly differences between people.
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  • sheldonklein
    sheldonklein Posts: 854 Member
    I assume OP's question translates as, is there a significant variance in the BMRs of people with comparable statistics (gender, weight and height). I understand there is minor variance except for a handful of outliers, but I stand ready to be persuaded otherwise.
  • vismal
    vismal Posts: 2,463 Member
    I think a lot of this comes down to genetics and medical issues (if any are present). The classic ectomoph, mesomorph and endomorph people. As strong_curves talked about, there certainly are people that have a MUCH easier time maintaining a healthy weight (naturally thin folks) and those that have MUCH easier time building muscle (usually also gaining fat). It's a spectrum. On the extremes you see the elite athletes -- whether it's a marathon runner on one side or powerlifters on the other. They no doubt are genetic freaks -- just like any elite athlete. That's not to say they don't work hard -- of course, they do -- but they have certain genetics that allow them to reach that level. Not everyone could work as hard and get those same results -- it's just not how the world works.

    So, it's all about being the best YOU. Being the best version of your genetic potential. So you may struggle more with weight loss/management or you may struggle more with gaining weight/muscle. Depending on your issues, certain strategies may work better or worse for you --- whether that's adjusting macros (carbs especially), using an intermittent fasting regime like 16:8 or 5:2, calorie cycling, etc. Deficits work for those without medical issues, but how you create that deficit may yield dramatically different results depending on your individual circumstances. A lot of it is trial and error figuring out what works best for you. But, yes, there are undoubtedly differences between people.

    While I don't have an issue with the rest of your post, somatotypes have been widely debunked.
    Agree. There is no science to support somatotypes.

    To answer the OP. Metabolism varies from person to person. There is a normal range that most people fall in to. The vast majority of people who claim they have weight issues due to slow metabolism simply eat to much. The vast majority of "hard gainers" who claim they cannot gain weight due to metabolism simply don't eat enough. Regardless of how much they claim to eat or not eat, unless you observe them 24 hours a day, what they say is meaningless. People lie, they miscalculate, they over and under estimate. There are several studies to prove that people are notoriously bad at calorie counting and estimating the calories found in meals. While it's true that those who fall to the low or high end of normal may have a slightly more challenging weight loss/gain experience, they are not so far from the average that their calorie goal should be unreasonably low or high. There are also those that fall outside of a normal range. They are outliers. While they do occur, they are the exception, not the rule. The vast majority of people claiming that slow or fast metabolism is the reason their goals are alluding them are making excuses, and possibly convincing themselves that their failure is out of their control. This is an extremely common defense mechanism. It should also be noted that those who fall a fair margin beyond normal deviation probably have some medical condition(s) causing their extreme deviation. Many of the conditions that can cause this are treatable. These people probably make up less then 1% of the population.
  • lindsey1979
    lindsey1979 Posts: 2,395 Member
    I think a lot of this comes down to genetics and medical issues (if any are present). The classic ectomoph, mesomorph and endomorph people. As strong_curves talked about, there certainly are people that have a MUCH easier time maintaining a healthy weight (naturally thin folks) and those that have MUCH easier time building muscle (usually also gaining fat). It's a spectrum. On the extremes you see the elite athletes -- whether it's a marathon runner on one side or powerlifters on the other. They no doubt are genetic freaks -- just like any elite athlete. That's not to say they don't work hard -- of course, they do -- but they have certain genetics that allow them to reach that level. Not everyone could work as hard and get those same results -- it's just not how the world works.

    So, it's all about being the best YOU. Being the best version of your genetic potential. So you may struggle more with weight loss/management or you may struggle more with gaining weight/muscle. Depending on your issues, certain strategies may work better or worse for you --- whether that's adjusting macros (carbs especially), using an intermittent fasting regime like 16:8 or 5:2, calorie cycling, etc. Deficits work for those without medical issues, but how you create that deficit may yield dramatically different results depending on your individual circumstances. A lot of it is trial and error figuring out what works best for you. But, yes, there are undoubtedly differences between people.

    While I don't have an issue with the rest of your post, somatotypes have been widely debunked.

    Yes and no. Don't you think at the very least they demonstrate the spectrum of genetic predisposition -- that there are some people who are fairly naturally thin and that comes rather easily to them and there are other where gain (muscle and fat) comes fairly easy? I wouldn't get into the rest of the theory, but I think as far as that goes, it's true.

  • Unknown
    edited September 2015
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  • vismal
    vismal Posts: 2,463 Member
    I think a lot of this comes down to genetics and medical issues (if any are present). The classic ectomoph, mesomorph and endomorph people. As strong_curves talked about, there certainly are people that have a MUCH easier time maintaining a healthy weight (naturally thin folks) and those that have MUCH easier time building muscle (usually also gaining fat). It's a spectrum. On the extremes you see the elite athletes -- whether it's a marathon runner on one side or powerlifters on the other. They no doubt are genetic freaks -- just like any elite athlete. That's not to say they don't work hard -- of course, they do -- but they have certain genetics that allow them to reach that level. Not everyone could work as hard and get those same results -- it's just not how the world works.

    So, it's all about being the best YOU. Being the best version of your genetic potential. So you may struggle more with weight loss/management or you may struggle more with gaining weight/muscle. Depending on your issues, certain strategies may work better or worse for you --- whether that's adjusting macros (carbs especially), using an intermittent fasting regime like 16:8 or 5:2, calorie cycling, etc. Deficits work for those without medical issues, but how you create that deficit may yield dramatically different results depending on your individual circumstances. A lot of it is trial and error figuring out what works best for you. But, yes, there are undoubtedly differences between people.

    While I don't have an issue with the rest of your post, somatotypes have been widely debunked.

    Yes and no. Don't you think at the very least they demonstrate the spectrum of genetic predisposition -- that there are some people who are fairly naturally thin and that comes rather easily to them and there are other where gain (muscle and fat) comes fairly easy? I wouldn't get into the rest of the theory, but I think as far as that goes, it's true.
    I don't really. In my opinion 90% of "ectomorphs" simply eat less then they think, 90% of "endomorphs" eat more than they think, and the vast majority of "mesomorphs" eat an appropriate amount of calories and probably regularly work out. Take myself for example. Look at me 4 years ago and my body SCREAMS endomorph. Almost all the classic traits. Look at me now and people who didn't know me from before would claim I was a mesomorph. There is just no science to support it. Sure different people naturally burn more/less calories per day, but the vast majority fall into the "normal" range.

  • Alluminati
    Alluminati Posts: 6,208 Member
    edited September 2015
    I think a lot of this comes down to genetics and medical issues (if any are present). The classic ectomoph, mesomorph and endomorph people. As strong_curves talked about, there certainly are people that have a MUCH easier time maintaining a healthy weight (naturally thin folks) and those that have MUCH easier time building muscle (usually also gaining fat). It's a spectrum. On the extremes you see the elite athletes -- whether it's a marathon runner on one side or powerlifters on the other. They no doubt are genetic freaks -- just like any elite athlete. That's not to say they don't work hard -- of course, they do -- but they have certain genetics that allow them to reach that level. Not everyone could work as hard and get those same results -- it's just not how the world works.

    So, it's all about being the best YOU. Being the best version of your genetic potential. So you may struggle more with weight loss/management or you may struggle more with gaining weight/muscle. Depending on your issues, certain strategies may work better or worse for you --- whether that's adjusting macros (carbs especially), using an intermittent fasting regime like 16:8 or 5:2, calorie cycling, etc. Deficits work for those without medical issues, but how you create that deficit may yield dramatically different results depending on your individual circumstances. A lot of it is trial and error figuring out what works best for you. But, yes, there are undoubtedly differences between people.
    Yeah. I thought somatotypes weren't a thing.
  • queenliz99
    queenliz99 Posts: 15,317 Member
    edited September 2015
    Alluminati wrote: »
    I think a lot of this comes down to genetics and medical issues (if any are present). The classic ectomoph, mesomorph and endomorph people. As strong_curves talked about, there certainly are people that have a MUCH easier time maintaining a healthy weight (naturally thin folks) and those that have MUCH easier time building muscle (usually also gaining fat). It's a spectrum. On the extremes you see the elite athletes -- whether it's a marathon runner on one side or powerlifters on the other. They no doubt are genetic freaks -- just like any elite athlete. That's not to say they don't work hard -- of course, they do -- but they have certain genetics that allow them to reach that level. Not everyone could work as hard and get those same results -- it's just not how the world works.

    So, it's all about being the best YOU. Being the best version of your genetic potential. So you may struggle more with weight loss/management or you may struggle more with gaining weight/muscle. Depending on your issues, certain strategies may work better or worse for you --- whether that's adjusting macros (carbs especially), using an intermittent fasting regime like 16:8 or 5:2, calorie cycling, etc. Deficits work for those without medical issues, but how you create that deficit may yield dramatically different results depending on your individual circumstances. A lot of it is trial and error figuring out what works best for you. But, yes, there are undoubtedly differences between people.

    Yeah. I thought somatotypes weren't a thing.

    Yea confusing
  • Kalikel
    Kalikel Posts: 9,603 Member
    Metabolism is just a concept, not a single thing. It's the end result of everything built up and broken down.

    If your body burns through calories faster or slower than a typical body, you'll be thinner or fatter than a typical person (similar - age, height, etc.) who eats the same amount.

    Thyroid hormone is one thing that most people have heard of that has a big effect on one's metabolism. Hyperthyroid people are often very skinny and hypothyroid people are frequently fat. You could have two people of the same height, weight, age, race, etc. and they could eat the same amount of calories and one would end up losing while the other gained. Theoretically, anyway.

    Lots of things affect how your body works.

    You look young. If you're really interested in it and want to learn about it, you should take some classes. If you enjoy learning this stuff, you might love those classes! :)
  • psuLemon
    psuLemon Posts: 38,432 MFP Moderator

    I think a lot of this comes down to genetics and medical issues (if any are present). The classic ectomoph, mesomorph and endomorph people. As strong_curves talked about, there certainly are people that have a MUCH easier time maintaining a healthy weight (naturally thin folks) and those that have MUCH easier time building muscle (usually also gaining fat). It's a spectrum. On the extremes you see the elite athletes -- whether it's a marathon runner on one side or powerlifters on the other. They no doubt are genetic freaks -- just like any elite athlete. That's not to say they don't work hard -- of course, they do -- but they have certain genetics that allow them to reach that level. Not everyone could work as hard and get those same results -- it's just not how the world works.

    So, it's all about being the best YOU. Being the best version of your genetic potential. So you may struggle more with weight loss/management or you may struggle more with gaining weight/muscle. Depending on your issues, certain strategies may work better or worse for you --- whether that's adjusting macros (carbs especially), using an intermittent fasting regime like 16:8 or 5:2, calorie cycling, etc. Deficits work for those without medical issues, but how you create that deficit may yield dramatically different results depending on your individual circumstances. A lot of it is trial and error figuring out what works best for you. But, yes, there are undoubtedly differences between people.

    While I don't have an issue with the rest of your post, somatotypes have been widely debunked.

    Yes and no. Don't you think at the very least they demonstrate the spectrum of genetic predisposition -- that there are some people who are fairly naturally thin and that comes rather easily to them and there are other where gain (muscle and fat) comes fairly easy? I wouldn't get into the rest of the theory, but I think as far as that goes, it's true.

    For a large part people arent naturally thin, just like people are naturally fat. For a large part those who are more thin tend to develop or have learned good eating habits and eat the right types of food to enable that. On top of that, some people naturally are more active than others.

    OP, @vismal gave a lot of solid information. I would like to add the your bmr tends to account for roughly 75% of the calories you burn. Outside of bmr/rmr there is thermal effect of food (calories burn through digestion), thermal effect of activities (calories burned through exercise), and non exercise adaptive thermogenesis (calories burned from daily activity).

    Ultimately people try to put a lot of stake in metabolism but what they should concentrate on more is Total Daily Energy Expenditure as this is your maintenance point. This is the point you either eat at, form a deficit or a surplus based on your goals. You can find it by tracking calories for 4+ weeks.
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