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  1. #1
    L8Bloomer's Avatar
    L8Bloomer is offline Junior Member
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    How is dietary saturated fat handled?

    Primal Fuel
    I'm sorry if this has been covered before. I've spent a few hours searching MDA and can't find an answer to this specific question.

    I've heard it said that "dietary fat doesn't make you fat" (and I'm a believer, having already lost 5 lbs not two weeks into my Primal diet). I've researched and read all about glucose and how it ends up being stored as fat. I've seen the biochemistry in detail (thanks, Robert Lustig). So far, so good. My question is: what happens to dietary fat (let's say, saturated fat) after you eat it? Can someone trace its path through the body for me?

    Where I'm getting confused (when asked by well-meaning friends) is how the animal fats I'm eating don't end up as fat on my butt, but all the carbs and sugars I was eating evidently did. They ask: even if you are attempting to use fat as your energy source, rather than glucose, won't it ultimately still depend on how much you exercise (the old "burn it or wear it" argument)?

  2. #2
    ProtoAlex's Avatar
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    The food goes in and gets broken down to differing sizes based on various enzymes in your gut, passed into your system and distributed according to built in pathways. The issue you're having is with falling for the basic assumption that most people have when it comes to nutrition. When you eat a turkey leg you don't grow an additional leg; when you eat chicken livers it doesn't only go to nourishing your liver, and when you drink a Pepsi you don't start sprouting an aluminum can somewhere in your body. The same goes for things like fats, proteins and carbs (to an extent). Fats and proteins are indeed used as building blocks in your system but many of them are so torn apart by the digestive enzymes mentioned above that they can be sent to many different places to build many different structures. When you consume too much of this some may be stored for later but the vast majority of it that is not used gets deposited next time you visit the commode.

    Carbohydrates unfortunately only really have one purpose and that's to provide quick energy. It's also severely toxic and life threatening in large enough concentrations in your blood. Because of it's potential life ending effects the body has to work to get the stuff out of commission (see insulin) Additionally your body is pretty darned good at storing carbs for later usage. Some is stored as glycogen however the primary storage location for excessive carbohydrates is fat cells. Fat cells are our bodies storage sites, they're not just places where last night's steak trimmings ended up clumping together.

    Things really start getting shifty once insulin resistance enters the picture which you run the risk of if you're in a chronically insulin heavy state.
    "You can demonstrate the purpose and limits of human digestion with a simple experiment: eat a steak with some whole corn kernels, and see what comes out the other end. It won’t be the steak."
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    The answer is that either can end up as fat or not, depending on what the body is going to do with them. If you eat fats you might store fats, or you might burn them before storing them, but either way you are going to burn them eventually, hopefully. I never understood the "oh noes we're storing fat, that makes us fat" thing. You don't get fat because you have stored fat as adipose, you get fat because you don't burn the fat that you have stored. Carbohydrate isn't special in this respect. It can be turned to fat via the de novo lipogenesis pathway in the liver, or it can be oxidized in the cells. If it is oxidized in the cells, that is cellular respiration that isn't involving fats. Either way we only have so many mitochondria and they always have to be burning something. if not one then the other.

    I think that low carb diets help people eat less food, but also in the first few months they reduce the de novo lipogenesis process in people who are overweight and whose insulin sensitivity isn't very good so they tend to convert carbohydrate in the blood stream to fat to get rid of it, since their insulin is having a tough time getting it into the cells and high blood sugar is toxic, it's like a panic response. The de novo lipogenesis process isn't bad because it is storing fat, it is bad because that fat tends to circulate in the blood for a while (serum triglycerides) and it tends to block leptin (our energy-communication hormone) from signaling to the brain to increase metabolism and decrease appetite. Also high blood sugar from poor glucose tolerance + lots of carbs is very inflammatory and that also ends up interfering with leptin signaling.

    Metabolism is complicated and I only have a cursory understanding of this stuff, but the main message is that macronutrients as a whole aren't necessarily fattening, it's all about what the body does with them. Some variations of macronutrients affect what the body does with them like table sugar and vegetable oil but the carbs in sweet potatoes or the fats in butter aren't going to be fattening if the body handles them properly. With either carbs or fats you will have to "exercise" in proportion to your intake of energy or you will accumulate fat. Exercise can mean a lot of things though. It could mean walking at the mall, hill-sprints, tapping your foot as you sit, or exercising your thermogenic mechanisms to produce heat. A healthy metabolism enables the possibility of "exercising" more as the brain is able to authorize the stimulation of the endocrine system to increase activity if required. What is apparent is that if someone is just sitting in a chair their fat-burning potential is greatly decreased, it's just not going to happen very well. Get up and go for best results and combine it with a health-centered approach that is going to optimize the ability of your metabolic mechanisms to do their job. I'm sorry I wish it was as simple as just not eating one type of macronutrient but a whole heck of a lot of people who only focus on that don't reach their goals. Some do but that's the exception, not the role. It's a good thing that around here we work on getting healthy first.
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  4. #4
    Thor Falk's Avatar
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    Quote Originally Posted by L8Bloomer View Post
    I'm sorry if this has been covered before. I've spent a few hours searching MDA and can't find an answer to this specific question.

    I've heard it said that "dietary fat doesn't make you fat" (and I'm a believer, having already lost 5 lbs not two weeks into my Primal diet). I've researched and read all about glucose and how it ends up being stored as fat. I've seen the biochemistry in detail (thanks, Robert Lustig). So far, so good. My question is: what happens to dietary fat (let's say, saturated fat) after you eat it? Can someone trace its path through the body for me?

    Where I'm getting confused (when asked by well-meaning friends) is how the animal fats I'm eating don't end up as fat on my butt, but all the carbs and sugars I was eating evidently did. They ask: even if you are attempting to use fat as your energy source, rather than glucose, won't it ultimately still depend on how much you exercise (the old "burn it or wear it" argument)?
    To extremely oversimplify: based on the metabolic options, carbs get stored as glycogen, or fat. Protein gets stored as muscle, or glycogen, or fat. Fat gets stored as fat. This is less relevant than it looks though, as the only storage that can be tapped with any meaningful volume (unless you are exercising extremely heavily) is fat.

    So ultimately, most of the excess calories end up being stored as fat - and as perviously pointed out, for fat-loss it is key to be able to mobilise those stores

  5. #5
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    Long-chain or medium-chain saturated fats?
    "Thanks to the combination of meat, calcium-rich leaf foods, and a vigorous life, the early hunter-gatherers were robust, with strong skeletons, jaws, and teeth." - Harold McGee, On Food And Cooking: The Science and Lore of the Kitchen

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