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  1. #1
    wiltondeportes's Avatar
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    Fat Metabolism/Digestion

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    Well, carbohydrate metabolism is much discussed primal and paleo circles. I think that's kind of the key to unlocking fat metabolism and loss for those that want/need to do so. I get why starch>glucose>fructose and sucrose in general terms. I think fat metabolism is a topic less discussed. I found myself asking how that works inside your body. What energy do I derive from any amount of fat I eat, and how? I know that the body can convert fat into glucose which then fills your muscles back up when they get deprived. But, muscles are not the only thing in your body using fuel. So what is it that makes my body need 2000-3000 calories? Where exactly does my dietary fat go from the food being ingested to the energy being burned??

    I will start the discussion with a link I found.
    Fat Digestion

    The type of fat does matter. The body first metabolizes carbs then protein,
    and while the protein is being metabolized, the body starts breaking down
    the fat and glycogen stores to convert it to fuel. Glycogen is a long
    string of simple carbohydrates, which gets cleaved and then the carbs
    (sugars) enter Glycolysis, which is the metabolic pathway by which we
    metabolize sugars.

    Fat, however, does not have the same chemical structure as sugars, but
    miraculously, the body breaks it down into the same product as which
    Glycolysis breaks down sugars. This product is called Acetyl-Co-A, which is
    a very small molecule from which we ultimately derive a bit of our
    energy. It of course, does this through a completely different metabolic
    pathway called beta-oxidation.
    Please add to my understanding.

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    Pitter's Avatar
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    Quote Originally Posted by wiltondeportes View Post
    I know that the body can convert fat into glucose which then fills your muscles back up when they get deprived.
    Fat does not actually participate in the process of being converted to glucose. When referring to gluconeogenisis, that's the process of the body using proteins to convert into glucose. Sugar in the bloodstream may be converted to fat for storage, but fat cannot be converted back to sugar (glucose) later for fuel.

    Quote Originally Posted by wiltondeportes View Post
    But, muscles are not the only thing in your body using fuel. So what is it that makes my body need 2000-3000 calories?
    your metabolism is the total energy that your body uses do cover all its internal processes of breakdown and repair as well as all your functions of daily living and activities. So, in that context of the whole body, it's not just muscles that need energy but other organs, digestion, healing, breathing, and so on. Everyone has a basal metabolic rate that just covers how much energy you'd need to just stay alive, then on top of this is added your level of activity and that adds up to your estimated calorie requirements.

    Quote Originally Posted by wiltondeportes View Post
    I found myself asking how that works inside your body. What energy do I derive from any amount of fat I eat, and how?
    Fats used for fuel in your body come from fats ingested in your diet, stored adipose tissue, carbohydrates (that couldn't be used as glucose or stored as glycogen in the liver or muscles).

    While carbs can be broken down very quickly for energy, only a small amount can be stored, which leads to the carb roller coaster and needing to eat frequent meals to keep blood sugar levels up that we all are wanting to avoid. Fats, on the other hand take longer to break down, but actually result in more energy (9 calories per grams vs. 4 cals per gram for carbs). Fats also are not a restricted energy source the way carbs are because the body stores so much more fat.

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    Edje Noh's Avatar
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    I would like a good source on the topic of beta-oxidation as well. Doug Mcguff explained it a bit in his talk at the 21convention (http://www.youtube.com/watch?v=2PdJFbjWHEU), but I'd like to now more of the specifics aswell.
    Last edited by Edje Noh; 06-04-2011 at 02:23 AM.

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    wiltondeportes's Avatar
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    Quote Originally Posted by Pitter View Post
    your metabolism is the total energy that your body uses do cover all its internal processes of breakdown and repair as well as all your functions of daily living and activities. So, in that context of the whole body, it's not just muscles that need energy but other organs, digestion, healing, breathing, and so on. Everyone has a basal metabolic rate that just covers how much energy you'd need to just stay alive, then on top of this is added your level of activity and that adds up to your estimated calorie requirements.



    Fats used for fuel in your body come from fats ingested in your diet, stored adipose tissue, carbohydrates (that couldn't be used as glucose or stored as glycogen in the liver or muscles).

    While carbs can be broken down very quickly for energy, only a small amount can be stored, which leads to the carb roller coaster and needing to eat frequent meals to keep blood sugar levels up that we all are wanting to avoid. Fats, on the other hand take longer to break down, but actually result in more energy (9 calories per grams vs. 4 cals per gram for carbs). Fats also are not a restricted energy source the way carbs are because the body stores so much more fat.
    I don't think that answers my question. Calories are determined by how much heat the food produces when it is burned. Our stomach is not a furnace literally (although you could call it that figuratively). My point is that the calorie hypothesis is false. I feel like I have a handle on how much protein I need (1g/lb of bodyweight to build muscle). Protein seems fairly simple since its primary objective is repair soft tissue. You can see what happens when you eat more or less of it. Carbohydrates seem to be fairly understandable too. We can eat them, and send those sugars to our muscles (well...the long answer is it depends on the sugar, but you get the idea). Or, our body can produce them if we don't eat them. This is done by converting fat or protein to glucose. I feel like I have a good grasp on what I must eat in a day to feel good and satisfy my soft tissue repairing as well as my muscle's glycogen.

    What I have not established is how much fat I must eat in a day and what I am even satisfying when I do this. I know you could give me grams of fat that people quote based off of % of calories needed or just a raw number people spout off. I want to know WHY. Where does it go? What happens when I eat less and what happens when I eat more than I need? Don't just say I'll gain weight because my metabolism is stellar. There's evidence of people who resisted gaining significant weight until their daily calorie intake was over 500% of the normal or something crazy. In other words, metabolisms can adapt to extra food being thrown in it. My goal is to eat efficiently and not (quite literally) poop my money away. I figure efficiency is best in the long run for health too.

    One last part. I know this is getting off topic. Respond to that previous paragraph first. I'm a big Herschel Walker fan. He's one of the more influential people I have read about when it comes to health. He got me doing bodyweight exercises last summer before I ever had read about Mark Sisson's lift heavy weights program of 5 bodyweight exercises. I never even did them consistently, but I was gaining real strength on top of what I already had (which was a pretty solid base...I squatted over twice my weight back in high school). Anyways, Herschel Walker describes his diet as one meal a day at night with varying reports on the quantity. Some indicate his caloric load was really not all that great. I figure I probably eat more food than he did if the report is correct. He was 6' 220 lb in his prime (and still is). So I wonder if it may be possible to program your genes to be more efficient users of these fats, proteins, and carbs. I go back to fats because that's really the main piece that I don't understand from a chemistry perspective yet.

  5. #5
    wiltondeportes's Avatar
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    Any help? This thread kind of got buried.

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    PCwizCube's Avatar
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    A couple of weeks ago I posted a thread asking about how fat is metabolized for energy as opposed to glucose. It probably doesn't answer all of your questions but you might learn from some of the thread. Basically it adds on to what is done with the fat after beta oxidiation.

    Fat preferred fuel over carbohydrates - Why? (Biochemically) - (go to last post for my interpretation of how fat is broken down for energy)
    http://www.marksdailyapple.com/forum/thread30950.html

    Sorry I can't add much information as I am wondering about the same things you are but I I hope that helps at least a little bit!

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    js290's Avatar
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    Quote Originally Posted by wiltondeportes View Post
    Well, carbohydrate metabolism is much discussed primal and paleo circles. I think that's kind of the key to unlocking fat metabolism and loss for those that want/need to do so. I get why starch>glucose>fructose and sucrose in general terms. I think fat metabolism is a topic less discussed. I found myself asking how that works inside your body. What energy do I derive from any amount of fat I eat, and how? I know that the body can convert fat into glucose which then fills your muscles back up when they get deprived. But, muscles are not the only thing in your body using fuel. So what is it that makes my body need 2000-3000 calories? Where exactly does my dietary fat go from the food being ingested to the energy being burned??

    I will start the discussion with a link I found.
    Fat Digestion



    Please add to my understanding.
    You're kind of all over the place... ingested fat does not get turned into glucose. Ingested fat either gets burned (lipolysis) or stored. Burning fat is easy: keep serum insulin levels low.

    The Blog of Michael R. Eades, M.D. Tips & tricks for starting (or restarting) low-carb Pt I


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    Quote Originally Posted by wiltondeportes View Post
    I don't think that answers my question. Calories are determined by how much heat the food produces when it is burned. Our stomach is not a furnace literally (although you could call it that figuratively). My point is that the calorie hypothesis is false. I feel like I have a handle on how much protein I need (1g/lb of bodyweight to build muscle). Protein seems fairly simple since its primary objective is repair soft tissue. You can see what happens when you eat more or less of it. Carbohydrates seem to be fairly understandable too. We can eat them, and send those sugars to our muscles (well...the long answer is it depends on the sugar, but you get the idea). Or, our body can produce them if we don't eat them. This is done by converting fat or protein to glucose. I feel like I have a good grasp on what I must eat in a day to feel good and satisfy my soft tissue repairing as well as my muscle's glycogen.
    If that didn't answer your question, then I don't think you asked what you wanted to know. Also, I wasn't telling you the cals/gram because of cals in and cals out. I was telling you to emphasize that the different fuels provide energy differently.

  9. #9
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    Quote Originally Posted by js290 View Post
    You're kind of all over the place... ingested fat does not get turned into glucose. Ingested fat either gets burned (lipolysis) or stored. Burning fat is easy: keep serum insulin levels low.

    The Blog of Michael R. Eades, M.D. Tips & tricks for starting (or restarting) low-carb Pt I

    I really like that McGraw guy. It was an interesting video. I understand in practice how to burn fat that you eat, but I STILL don't understand how your body burns that fuel. Lipolysis doesn't magically burn fat into heat energy which it simply distributes throughout the body to stay warm....I assume. So, what exactly is going on? I realize this is a simple question with a complicated answer, but I can only ask...

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