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Thread: Metabolism - how much does it vary?

  1. #1 Metabolism - how much does it vary? 
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    I have been on a diet. The subject has come up in discussion with other dieters, of how many calories you need to eat per day, in order to lose a certain amount of weight. In my case, I have found this table to be quite accurate. I think it is based on numbers published by the USDA.

    http://www.dietbites.com/Pyramid-Die...ire-index.html

    Knowing that a pound of fat equals 3500 calories, you can figure that if you eat 500 calories per day less than what is listed in the table, you will lose a pound per week.

    In my case, this works out almost exactly. However, other dieters have said their metabolism is such that they burn far less calories. I wonder if that is really true, or if perhaps they are not keeping good enough track of their intake.

    So, how much can it really vary?


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  3. #2  
    Moderator Moderator TheBiologista's Avatar
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    I gather from the bits and pieces I've read that there's not a huge variation and that the "I've got a slow metabolism" argument (or opposite) used by some to justify general build doesn't really hold all that well. The main determinants for metabolism rate seem to be age (slower as we get older) and size (faster for larger people). But I'm really not sure how much of a range of rates we're talking about.


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  4. #3  
    Reptile Dysfunction drowsy turtle's Avatar
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    I can eat up to around 4000-4500 calories per day and my weight does not change.

    On the other hand, I could reduce this to 2500 per day, and my weight still does not change.


    My weight only significantly decreases if I reduce my intake to around 2000 calories per day.

    This has lead me to believe that your metabolism is more flexible than diets generally allow for.
    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
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  5. #4  
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    Quote Originally Posted by TheBiologista
    The main determinants for metabolism rate seem to be age (slower as we get older) and size (faster for larger people).
    Just what I was going to say. I don't know all that much about metabolism in general, but I would first suspect that there is bound to be some differences in how we metabolize things.

    Evidence that might justify my statement might come from various studies for example, CypP450 enzymes and drug metabolism. But then I came up with a counter argument, polymorphisms for enzymes in liver metabolism might not have a dramatic effect thus allow the person to live normally, but similar polymorphisms in food metabolism might well result in fatal consequences.

    But I suppose it is possible for a person to have multiple functional alleles resulting in a better coping capacity?

    My basic point would be that I would assume there are some differences, but in truth I think they balance out over all.

    Edit:

    Reference to one study I referred too, haven't covered it much in detail yet, so if I have completely miss-interrupted it my apologies. I gather that it is looking at some genetic differences in metabolism.

    Polymorphic Human Cytocrhome P450 enzymes: an opportunity for individual drug treatment.

    Trends in Pharmacological Sciences 20: 342 -349, 1999
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  6. #5  
    Forum Cosmic Wizard i_feel_tiredsleepy's Avatar
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    Quote Originally Posted by TheBiologista
    I gather from the bits and pieces I've read that there's not a huge variation and that the "I've got a slow metabolism" argument (or opposite) used by some to justify general build doesn't really hold all that well. The main determinants for metabolism rate seem to be age (slower as we get older) and size (faster for larger people). But I'm really not sure how much of a range of rates we're talking about.
    In general this is true, but abnormal hormone levels, like hypethyroidism, can affect weight lost.
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  7. #6 Re: Metabolism - how much does it vary? 
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    Quote Originally Posted by Harold14370
    So, how much can it really vary?
    That table is better suited to reptiles, who needn't burn calories for body heat. I think, Harold14370, as an engineer you appreciate how maintainance of constant internal temperature must depend on the rate of heat dissipation. Remove the sweater, turn down the thermostat - you *must* burn more, even just sitting at the computer or while you sleep.
    A pong by any other name is still a pong. -williampinn
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  8. #7  
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    Depends on your genetic makeup. Africans tend to have a rapid metabolism which they need to flush out the toxins they come into contact with everyday. (Source: Survival of the Sickest by Sharon Maoleem)
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