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How much fat do we burn while sedentary?
Any idea what fat/carb ratio the body burns while resting?
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depends on your build, diet, level of fitness, amount of activity, etc, etc...
It's a long list. |
Alright, ballpark couch potato. What is it and is it more fat to carbs burned while sleeping if you're fit or less fat to carbs?
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A ballpark figure is that the human body will burn 10 calories per pound of lean body mass doing basically nothing.
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I think the ratio is like 80% fat to 20% sugar at rest. It might even be higher than that. If I get a chance, I'll check my books, but it should be available via a google search.
Al |
Heh heh, that gives new meaning to "burn fat while you sleep." :D
I didn't think it was that high. |
It’s even higher than that; if you aren’t using your brain much, essentially all calories come from fat. This plot shows that even while doing light exercise most of the calories still come from free fatty acids or muscle triglycerides
http://i168.photobucket.com/albums/u...0intensity.jpg |
Very nice chart. On the brain thing, it turns out that the brain uses fewer calories while you watch TV than when you are asleep.
Al |
I must be terrible at googling 'cause I couldn't seem to come up with a page that explained it.
TV sucks. Bikeforums rocks! :D |
Originally Posted by Al.canoe
Very nice chart. On the brain thing, it turns out that the brain uses fewer calories while you watch TV than when you are asleep.
Some other study said that playing 'intense' video games expends about the same energy as walking at 2mph |
As far as I understand, the body doesn't begin to burn fat until it's run out of glucose stores. Generally, an "average" man will burn about 70-100 calories an hour doing no activity. A site like http://www.caloriesperhour.com/index_burn.html might provide you with more answers.
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Originally Posted by Swoop
As far as I understand, the body doesn't begin to burn fat until it's run out of glucose stores. Generally, an "average" man will burn about 70-100 calories an hour doing no activity. A site like http://www.caloriesperhour.com/index_burn.html might provide you with more answers.
A typical thin athlete will have something like 80,000 calories of stored fat, but only 1500 to 2000 calories of stored carbs to burn. If you didn't burn fat all the time, you couldn't function very long. Al |
Originally Posted by Al.canoe
When the body runs out of glucose, the brain is being starved and it will cause the body to convert muscle protein to glucose and reduce body activity to save itself. You can see from the chart that the body always burns fat.
A typical thin athlete will have something like 80,000 calories of stored fat, but only 1500 to 2000 calories of stored carbs to burn. If you didn't burn fat all the time, you couldn't function very long. Al The chart shows how fat burning takes place during exercise, not while sedentary. The brain is never starved of energy, it's a priority of the body to ensure there is always energy supplied, only the source of the energy may change. If you are suggesting that our bodies are constantly converting fat as an energy source, then you are suggesting a constant state of ketosis, which is dubious if not plain wrong. From here The liver stores glucose by converting it to glycogen. It holds perhaps a 12-hour supply of glucose in its glycogen. Once you finish digesting all of the carbohydrates that you last ate, the liver starts converting its stored glycogen back into glucose and releases it to maintain glucose in the blood. Lipolysis also starts breaking down fat in the fat cells and releasing fatty acids into the bloodstream. Tissues that do not need to use glucose for energy (for example, muscle cells) start burning the fatty acids. This reduces the glucose demand so that nerve cells get the glucose. Once the liver runs out of glycogen, the liver converts to a process called gluconeogenesis. Gluconeogenesis turns amino acids into glucose. The liver then begins producing ketone bodies from fatty acids being made available in the blood by lipolysis. Brain and nerve cells convert over from being pure consumers of glucose to partial consumers of ketone bodies for energy. This process is called ketosis -- which is why the Atkins plan is also known as a ketogenic diet. |
Swoop you have learned about carbohydrate metabolism, but lack understanding of the whole metabolic picture. The liver and pancreas work at tightly controlling blood sugar levels; this does not, however, mean that the body is burning carbohydrates preferentially. Read up on mitochondrial functioning. Furthermore gluconeogenesis only occurs during metabolically extreme events like starvation or when placed on a skewed macronutrient ratio diet (low carb).
http://i168.photobucket.com/albums/u...ismSummary.gif |
Originally Posted by Swoop
If you are suggesting that our bodies are constantly converting fat as an energy source, then you are suggesting a constant state of ketosis, which is dubious if not plain wrong.
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Originally Posted by Swoop
If you are suggesting that our bodies are constantly converting fat as an energy source, then you are suggesting a constant state of ketosis, which is dubious if not plain wrong.
From here The percentage of fat vs. carbs being used has already been posted by enthalpic. It's based upon the intensity of exercise and at a sedentary pace, most of the calories burnt by your body is fat. About 50 cal/hr is the figure I've heard most often. |
Okay, well everyone seems to know better than me so I concede. It didn't/doesn't make sense to me that the body burns fat when it's got fuel from what's been ingested, but if facts are facts so be it.
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Originally Posted by Swoop
Okay, well everyone seems to know better than me so I concede. It didn't/doesn't make sense to me that the body burns fat when it's got fuel from what's been ingested, but if facts are facts so be it.
Also, it helps to realize that, since we have a limited amount of food in our belly and glycogen in our muscles, it makes sense for the body to burn as much fat as it can during exertion. Our distant ancestors were more likely to survive if they could maintain heavy exertion for longer during a fight or a flight. Those that could were more likely to survive. :) |
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