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  • Fat used as energy during weight loss...

    If someone is used to eating a high carb low fat diet then they'll typically need to eat fairly often because their body is used to running on carbs. Now from my understanding, if that person switches over to a high fat low carb diet then their body will get used to using dietary fat for energy and it will be able to easily switch over to body fat when it's used up the food energy. So that means the body is eating food and then saturated fat (body fat) to make up the rest of its required energy. Could someone please confirm this for me?

    Now if someone was on a restricted calorie diet where they were only eating say 500 calories a day, they'd generally get tired and weak right? But why does this happen? Assuming they're getting all the vitamins and minerals they need and they're a bit overweight, why can't they easily use body fat for energy? And would this be easier for them if their diet was high in fat (but same amount of calories)?

  • #2
    Originally posted by Ribbons View Post
    If someone is used to eating a high carb low fat diet then they'll typically need to eat fairly often because their body is used to running on carbs. Now from my understanding, if that person switches over to a high fat low carb diet then their body will get used to using dietary fat for energy and it will be able to easily switch over to body fat when it's used up the food energy. So that means the body is eating food and then saturated fat (body fat) to make up the rest of its required energy. Could someone please confirm this for me?
    Dr Rosedale, a portion of Boston Speech at the Heinz Conference - YouTube

    Originally posted by Ribbons View Post
    Now if someone was on a restricted calorie diet where they were only eating say 500 calories a day, they'd generally get tired and weak right? But why does this happen? Assuming they're getting all the vitamins and minerals they need and they're a bit overweight, why can't they easily use body fat for energy? And would this be easier for them if their diet was high in fat (but same amount of calories)?
    Because it's about hormonal balance, not energy balance. The body doesn't burn calories; it burns adenosine triphosphate (ATP).

    The Science Behind The “Low Carb Flu”, and How To Regain Your Metabolic Flexibility - GNOLLS.ORG
    Fat Head Fat Mice And The Laws of Thermodynamics

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    • #3
      Thanks for the Fathead link, js290. I shared it on a lowcarb forum.
      Danni

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      • #4
        You will be no better at fasting eating a high fat/low carb diet than eating a high carb/low fat diet. People in the modern world have issues with fasting because they go through bouts of hypo- and hyperglycemia. Their hormones are disregulated because they're constantly grazing/snacking and eating poisonous foods that lack nutrition, like grains, sugars and legumes. Carbohydrates aren't the cause. Carbohydrates are the victim because most toxic foods tend to be high in carbs. If you ate a diet mostly made up of bananas, sweet potatoes and free range chicken, you'd be eating a high carb/low fat diet, but you'd be perfectly healthy, and you'd be no worse off than someone who ate steak and broccoli as dietary staples.

        Concentrate on eating real, whole foods and avoiding the problem foods the Primal Blueprint lays out and you'll be in great shape. There is no reason to avoid a potato or an apple if that's what you're truly craving. Your body is craving it for a reason. Just make sure you feed any sugar cravings with fruit or starch, not with grains, cakes, cookies and processed sugars. I actually recommend a moderate fat/moderate carbohydrate approach so your body is used to running on both fats for fuel and carbs for fuel. I eat fruit almost every day, but every once in awhile I'll throw a zero carb meal of steak and eggs with not a trace of vegetables at me, or 99% fat free ground turkey burgers with sweet potatoes without barely a trace of fat. And usually once a week I won't eat for a full 24 hours. Vary your diet and eat real, nutritious foods that promote a feeling of satiety and you'll have success.
        Last edited by ChocoTaco369; 05-11-2012, 10:34 AM.
        Don't put your trust in anyone on this forum, including me. You are the key to your own success.

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        • #5
          Originally posted by Ribbons View Post
          Now if someone was on a restricted calorie diet where they were only eating say 500 calories a day, they'd generally get tired and weak right? But why does this happen? Assuming they're getting all the vitamins and minerals they need and they're a bit overweight, why can't they easily use body fat for energy? And would this be easier for them if their diet was high in fat (but same amount of calories)?
          Insulin resistance also comes into play here. If you have higher circulating levels of insulin, due to resistance, fat burning is effectively turned off. Hormone (insulin) sensitive lipase, used to hydrolyze fatty acids, can't process the fat in the presence of insulin.

          This is why reducing carbohydrate intake and adding in resistance training together help unlock "fat burning" for people with deranged metabolisms.

          This is how I understand it...
          Last edited by Fernaldo; 05-11-2012, 12:22 PM.
          "The problem with quoting someone on the Internet is, you never know if it's legit" - Abraham Lincoln

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          • #6
            Originally posted by Fernaldo View Post
            Insulin resistance also comes into play here. If you have higher circulating levels of insulin, due to resistance, fat burning is effectively turned off. Hormone (insulin) sensitive lipase, used to hydrolyze fatty acids, can't unlock the fat in the presence of insulin.

            This is why reducing carbohydrate intake and adding in resistance training together help unlock "fat burning" for people with deranged metabolisms.
            Also, it may not be possible to burn both fat and glucose at the same time.

            The Glucose-Fatty Acid Cycle

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            • #7
              Originally posted by Ribbons View Post
              Now if someone was on a restricted calorie diet where they were only eating say 500 calories a day, they'd generally get tired and weak right? But why does this happen? Assuming they're getting all the vitamins and minerals they need and they're a bit overweight, why can't they easily use body fat for energy? And would this be easier for them if their diet was high in fat (but same amount of calories)?
              You are assuming someone would get tired and weak. They might get tired and weak at first and then they might start to feel better. If they are grossly overweight, they'd have lots of fuel to burn and might not need to eat much at all for a very long time.
              Features of a successful therapeutic fast of 382 days' duration -- Stewart and Fleming 49 (569): 203 -- Postgraduate Medical Journal
              Female, 5'3", 50, Max squat: 202.5lbs. Max deadlift: 225 x 3.

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              • #8
                Originally posted by Ribbons View Post
                Now if someone was on a restricted calorie diet where they were only eating say 500 calories a day, they'd generally get tired and weak right? But why does this happen? Assuming they're getting all the vitamins and minerals they need and they're a bit overweight, why can't they easily use body fat for energy? And would this be easier for them if their diet was high in fat (but same amount of calories)?
                Why? You have to ask? Because they want to live through the famine, that's why. If they burnt energy at the same rate as in good times, then yes, they would lose weight super quick while not feeling tired or weak at all. Then they would die. Real multi-year famines have happened in living memory in most parts of the world, including Europe.

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                • #9
                  Originally posted by billp View Post
                  Why? You have to ask? Because they want to live through the famine, that's why. If they burnt energy at the same rate as in good times, then yes, they would lose weight super quick while not feeling tired or weak at all. Then they would die. Real multi-year famines have happened in living memory in most parts of the world, including Europe.
                  +1
                  F 5 ft 3. HW: 196 lbs. Primal SW (May 2011): 182 lbs (42% BF)... W June '12: 160 lbs (29% BF) (UK size 12, US size 8). GW: ~24% BF - have ditched the scales til I fit into a pair of UK size 10 bootcut jeans. Currently aligning towards 'The Perfect Health Diet' having swapped some fat for potatoes.

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                  • #10
                    The way this kind of stuff works is more related to what the brain uses for fuel, not the body. When you either fast or eat a ketogenic style diet, your liver starts producing ketones in response to a drop in blood glucose. These ketones are being produced to fuel the brain since there is not enough glucose to go around and the brain can run pretty well on ketones. In order to make ketones, you have to release body fat as they are a byproduct of fatty acid oxidation. Your liver starts breaking down the fat and ketones make their way to the brain to fuel it. It normally takes a few days of really low carbohydrates to initiate this process and allow the brain to adapt to burning ketones for fuel if you have been higher carb. Another way to get your brain ketone adapted is using coconut oil, as it is instantly metabolized with ketones being the end product. After that your brain has access to any of the fuel it needs.

                    The primary problem with your standard calorie cutting diet is that it is impossible to fuel the brain on one. If the brain is using glucose as it's primary fuel it needs 150g for basic ops. If you eat a 1200 calorie diet that is 50% carbohydrate you are getting exactly 150g of carbohydrate so once you decide to do any exercise your brain senses low fuel and increases appetite. If your brain is ketone adapated, your brain never senses a low energy state because it has ketones for fuel and appetite stays low. Your brain controls everything, ultimately your survival is dependent on feeding it so your body starts burning fat to make ketones if you aren't providing enough via diet.

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                    • #11
                      Ah, ok thanks for all the replies. I'm still a little confused about it all because I'm 17 and somewhere between "healthy" and "overweight". I've been through periods of eating under 400-600 calories a day and fasting a lot, both after being used to a high carb high calorie diet and a mostly paleo low carb diet. I didn't do this just as an experiment; I was bordering on an eating disorder but I'm mostly over that now. I found that it was much easier to eat very little when most of my calories came from fat than from carbs, although I admit the carbs I used to eat were things like wholegrain pasta and rye bread, not starchy vegetables. I also want to add that sugar wasn't part of my diet for any of this, so I didn't have fructose messing with my hormones. Anyway, so what I noticed was that after the high carb diet when I fasted or didn't eat much, I was very close to fainting. I was always dizzy and weak. After the high fat diet I was pretty normal and I was satisfied with just tiny amounts of food.
                      By the way, the links some of you posted were very interesting so thanks for that.

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                      • #12
                        Originally posted by Ribbons View Post
                        although I admit the carbs I used to eat were things like wholegrain pasta and rye bread, not starchy vegetables.
                        Archevore - Archevore Blog - The Argument Against Cereal*Grains

                        Originally posted by Ribbons View Post
                        Anyway, so what I noticed was that after the high carb diet when I fasted or didn't eat much, I was very close to fainting. I was always dizzy and weak. After the high fat diet I was pretty normal and I was satisfied with just tiny amounts of food.
                        How Blood Sugar Control Works--And How It Stops Working
                        What is a Normal Blood Sugar?

                        Originally posted by Ribbons View Post
                        By the way, the links some of you posted were very interesting so thanks for that.
                        Best of luck in your quest for health, even at the indestructible age of 17. Keep learning.

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