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Does Body Fat percentage effect your metabolism?

Chiefkeef420Chiefkeef420 Member Posts: 11 Member Posts: 11
Just curious, does your resting metabolism increase if you have a lower body fat percentage and by how much?
Also how can I determine body fat percentage by appearance?
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Replies

  • Just_ScottJust_Scott Member Posts: 1,791 Member Posts: 1,791
    A group of folks on here will give you an approximation if you ask them. They will want several shots and they are fairly accurate with their estimates. Just search the thread and contact them.

    As for metabolism, I have no idea. I've dropped from 30.3 to 21.8 in body fat and could care less about resting metabolism as long as the body fat drops I'm a happy camper. Best of luck.
  • MityMax96MityMax96 Member, Premium Posts: 5,812 Member Member, Premium Posts: 5,812 Member
    Do a search for leptin.

    Read about that hormone, see if it answers your question.
  • SideSteelSideSteel Member Posts: 11,079 Member Member Posts: 11,079 Member
    Generally as you lose weight a combination of things happen:

    1) You have less weight to move around, which causes you to burn less calories.
    2) An adaptive response to dieting occurs (combination of hormonal downregulation, reduction in spontaneous activity) that further reduces your caloric expenditure.

    EDIT: But I don't think it's a cut-and-dry issue. For example if an obese sedentary individual lifts weights and diets down to a reasonable level of leanness and continues to train hard (I'm speaking in terms of years here, not days), I wouldn't be surprised to see an increase in total expenditure when you factor in the contribution from LBM and the massive upswing in activity going from "sits on the couch" to "trains like a beast".

    And I only mention the latter part of it for context.
  • _noob__noob_ Member Posts: 3,376 Member Member Posts: 3,376 Member
    generally speaking, your body does NOT like being lean.
  • neandermagnonneandermagnon Member Posts: 7,540 Member Member Posts: 7,540 Member
    the best way to think of this question, is that all the cells in your body need energy. so, more cells = you need more energy (higher basal metabolic rate (BMR)) = your metabolism is faster

    however, different cells need different amounts of energy. muscle cells and brain cells need a lot of energy, fat cells not so much, because they're just sitting around doing not so much, while your brain cells and muscle cells are working hard.

    so to answer your question more specifically....

    if the body fat percentage has gone up because you gained muscle mass, then your metabolism will be faster, because more muscle cells = you need more energy to keep the new cells going = faster metabolism

    however if your body fat percentage has gone down because you lost fat, then your metabolism will slow, because fewer fat cells = you don't need quite so much energy to keep all your cells alive. but fat cells don't burn as much as muscle, so the decrease in metabolism from fat loss is smaller than if you'd lost the same number of muscle cells.

    if both have happened (which can happen with noob gains etc), then the new muscle cells will be using more energy while the newly shrunk fat tissues will be using less energy. So your metabolism may be a bit faster or a bit slower, depending on the proportions of muscle gained to fat lost.


    Another angle to approach this question.... say you have two people of the same weight, but one has a lower body fat percentage than the other, the one with the lower body fat percentage would be expected to have a faster metabolism, because they have proportionally more lean mass (which includes more cells that work hard and burn more energy) and proportionally less fat (fat cells don't burn that much energy.

    There are other factors that affect the metabolism though, i.e. medical conditions, medication, the human body's adaptations to prolonged food shortages (i.e. prolonged insufficient food intake) can all affect the metabolism as well.

    One thing to realise though, is that the above things will result in small changes in the metabolism, if you are aiming to maximise the amount of calories you burn, then exercise and physical activity will burn far more than changes in your body composition (e.g. adding more lean mass) will. However they're not mutually exclusive... you can do both, i.e. increase your lean mass and increase your activity levels. And also, eat properly. I hate the term "starvation mode" but millions of years of evolution in favour of individuals who can survive food shortages, means that the human body is very good at adapting to insufficient food.... good news if you want to survive a famine, bad news if you're trying to lose body fat.
  • cwolfman13cwolfman13 Member Posts: 38,077 Member Member Posts: 38,077 Member
    The leaner you are, the less calories your body needs to maintain itself. That said, the more LBM you have, the faster your resting metabolism will be...so if you took a 180 Lb guy with 20% BF and a 180 Lb guy with 12% BF the leaner guy will have a slightly faster resting metabolism due to more LBM. But if you compared that same lean 180 Lb guy to a 250 Lb guy of relatively similar stats otherwise, the 250 Lb guy is going to burn more calories overall due to the shear mass that needs to be moved about just to perform daily stuff.
  • husseycdhusseycd Member Posts: 815 Member Member Posts: 815 Member
    The amount of lean muscle you have does affect your RMR. Look up the Katch-McArdle formulas for more information. I know I had my RMR tested and it was extremely close to the calculated RMR. For those that say it doesn't matter, I disagree. My RMR is 1580 calories/day (at 128 lbs and 19% BF). That adds into the overall amount I can eat. And since I do like food...
  • jonnythanjonnythan Member Posts: 10,217 Member Member Posts: 10,217 Member
    The leaner you are, the less calories your body needs to maintain itself.

    I believe you mean more.
  • bepeejayebepeejaye Member Posts: 775 Member Member Posts: 775 Member
    generally speaking, your body does NOT like being lean.
    Simple but perfectly put! :)
  • mike_nymike_ny Member Posts: 351 Member Member Posts: 351 Member
    In almost all cases, yes. More lean mass (especially muscle) requires more calories to maintain. Less fat cells affect leptin and insulin levels.

    And, leaner people tend to just be more active both as a cause and as a result of being leaner just like fatter people in general tend to be less active again both as a cause and result. You do get more energy just not having to carry the extra weight you used to have. Take whatever weight you've lost and put that in a backpack or as dumbbells and carry it around for a while and it's pretty obvious that carrying that extra weight was making you more tired and less active than you thought at the time.

    Another new factor in science being the hottest thing now is the effect of gut bacteria on metabolism. Eating a cleaner diet over a sustained period changes your ratio of gut bacteria colonies. So, eating the same foods in the same amounts can be digested, absorbed, and have different effects on that alone. That means that the occasional bad meal or bender after getting lean will probably not be as bad as it was back when you we're eating bad all the time. This also works the other way, though. Going back to eating crap will also change your gut bacteria ratios and putting you back in your pre-weight loss mode. This seems to have a pretty good correlation to yo-yo dieting where someone loses weight, maintains it for a while after going back to their old diet, and then starts gaining it all back.

    There are the exceptions where thyroid, hormones, or other triggers can have their own effects adding to the mix so,metabolism doesn't seem to play by the rules. We all know someone who can't gain weight as much as they eat and others who have a very hard time losing regardless of running deficits, but those are the minority. For most people, getting leaner has very positive effects on your metabolism.
  • momswansonmomswanson Member Posts: 76 Member Member Posts: 76 Member
    Absolutely....and I base this answer on emperical data! Two years ago I had by RMR tested by my doctor, you know, machines and all, and they determined that I was below average and that I needed to eat below 1200 if I wanted to lose weight. I have spent almost two years working at losing weight and working out and increasing my muscle mass and reducing my body fat. I had my RMR retested last week, and I am happy to say that according to the test, I need to eat 2000 calories just to maintain my weight, and I shouldn't eat any less than 1500 calories! I hope this helps!
  • cwolfman13cwolfman13 Member Posts: 38,077 Member Member Posts: 38,077 Member
    The leaner you are, the less calories your body needs to maintain itself.

    I believe you mean more.

    I'm much leaner than I used to be and I require fewer calories to maintain my weight than I used to simply because I weigh about 40 Lbs less. When I was fat I could maintain eating more calories than I do now and I didn't exercise...now I have to exercise just to be able to approach the amount of food I used to eat...and it's still not that close.

    That said, and I think I explained it...I'm about 180 Lbs and 19% BF...someone of the same stats but being 12% BF would actually require more calories because body weight is the same...but LBM would be substantially more.
  • jonnythanjonnythan Member Posts: 10,217 Member Member Posts: 10,217 Member
    The leaner you are, the less calories your body needs to maintain itself.

    I believe you mean more.

    I'm much leaner than I used to be and I require fewer calories to maintain my weight than I used to simply because I weigh about 40 Lbs less. When I was fat I could maintain eating more calories than I do now and I didn't exercise...now I have to exercise just to be able to approach the amount of food I used to eat...and it's still not that close.

    That said, and I think I explained it...I'm about 180 Lbs and 19% BF...someone of the same stats but being 12% BF would actually require more calories because body weight is the same...but LBM would be substantially more.

    You require fewer calories because you have 40lbs less mass, not because you are leaner.

    At a given weight, the leaner body will require more calories to maintain than the less lean body (all else being equal).

    So the correct statement is "The leaner you are, the MORE calories your body needs to maintain itself."
  • geekyjock76geekyjock76 Member Posts: 2,728 Member Member Posts: 2,728 Member
    Decreased fat mass is simply an outcome of calorie restriction, which affects one's metabolic proficiency and may have a lasting effect due to certain variables and conditions. An increase in lean mass, among other things, would lead to an increase in both resting and active metabolic rate.
  • lithezebralithezebra Member Posts: 3,684 Member Member Posts: 3,684 Member
    The less you weigh, the fewer calories you need to sustain your body weight and fuel your activity. The more you weigh, whether it's fat or muscle, the more calories you use to do the same things. Beyond that, there are no simple, uncontested answers.
  • BinaryPulsarBinaryPulsar Member Posts: 9,068 Member Member Posts: 9,068 Member
    This is just my personal experience, but it appears that I need to eat a lot more than most people that are the same size as me. If I don't, then I lose weight very rapidly that I don't want to lose. I still want to be lean, fit, with a good body composition. Lifting weights helps me to keep weight on in a sense because then I can maintain and build muscle. It seems the leaner I get, the more food I need to eat. I can eat less when my activity level decreases, but that usually only happens if I am dealing with something that is depressing (being active is an important part of my life).
  • firstsipfirstsip Member Posts: 8,578 Member Member Posts: 8,578 Member
    This is just my personal experience, but it appears that I need to eat a lot more than most people that are the same size as me. If I don't, then I lose weight very rapidly that I don't want to lose. I still want to be lean, fit, with a good body composition. Lifting weights helps me to keep weight on in a sense because then I can maintain and build muscle. It seems the leaner I get, the more food I need to eat. I can eat less when my activity level decreases, but that usually only happens if I am dealing with something that is depressing (being active is an important part of my life).

    ^ This and what johnnythan said.

    If someone is heavier and losing fat + muscle with just eating at a deficit, they will need gradually less calories and have a lower RMR.

    If someone is dropping body fat % but increasing (or even maintaining) a higher LBM than the first person, their RMR will be higher in order to maintain muscle.

    It's hard for the body to maintain a low bf%+LBM than it is to maintain a higher body fat %, and that "hardness" requires calories and work (strength training, activity, etc.).
  • QuietBloomQuietBloom Member Posts: 5,412 Member Member Posts: 5,412 Member
    Yes, but it has to do with your %Lean Body Mass, so it is indirectly related to body fat%. The more lean mass you have, the more metabolically active muscle you have, and the more calories you burn even at rest.
  • QuietBloomQuietBloom Member Posts: 5,412 Member Member Posts: 5,412 Member
    generally speaking, your body does NOT like being lean.
    Simple but perfectly put! :)

    I think everyone is different, and probably mostly has to do with genetics. I have always been fairly lean and so has my father. It is just our body type.
  • SteveJWatsonSteveJWatson Member Posts: 1,228 Member Member Posts: 1,228 Member

    You require fewer calories because you have 40lbs less mass, not because you are leaner.

    At a given weight, the leaner body will require more calories to maintain than the less lean body (all else being equal).

    So the correct statement is "The leaner you are, the MORE calories your body needs to maintain itself."

    Er, no - what you are driving at is that the greater your % LBM, the more calories you need to maintain. However, this is not the same as "the leaner you are" in this example. You are talking about two individuals at the same mass, but with differing muscle percentages. SS was meaning the same individual having lost mass (which could mostly be fat).

    For example: You start off at 250lbs and 35% bodyfat and diet to say 165lbs, 15% bodyfat - you will require far less energy to maintain your mass at 165lbs, 15% lbm than you did at 250lbs....
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