How does fat leave the body?

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How does fat leave the body?

Postby weakmagneto on July 28th, 2016, 1:39 am 

I'm sure that many people believe that fat leaves the body by being burned off in the form of heat or energy. But according to this article, we exhale most of it.

This has to be my favourite part of the article:

Even if one traces the fates of all the atoms in the body, the secret to weight loss remains the same: In order to lose weight, one needs to either eat less carbon or exercise more to remove extra carbon from the body.


Any thoughts or comments about this article?
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Re: How does fat leave the body?

Postby Watson on July 28th, 2016, 8:35 am 

I just saw a segment on Dr Oz on that very subject, I think Monday, but could be Tuesday if you look online CTV. I'll have to come back to this one later.
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Re: How does fat leave the body?

Postby SciameriKen on July 28th, 2016, 9:07 am 

weakmagneto » Thu Jul 28, 2016 5:39 am wrote:I'm sure that many people believe that fat leaves the body by being burned off in the form of heat or energy. But according to this article, we exhale most of it.

This has to be my favourite part of the article:

Even if one traces the fates of all the atoms in the body, the secret to weight loss remains the same: In order to lose weight, one needs to either eat less carbon or exercise more to remove extra carbon from the body.


Any thoughts or comments about this article?



This is just a fancier way of saying to lose weight you must simply have calories in < calories out. Weight loss is far more complicated than that. Still on just a pure reductionist viewpoint I'd rate it as "mostly true", with perhaps a slight contribution of weight loss coming from water loss and skin/hair flaking off.
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Re: How does fat leave the body?

Postby Braininvat on July 28th, 2016, 9:13 am 

I would note that "eat less carbon" simply means "eat less food." Anything that qualifies as food is molecules built on a carbon chain. Fat, like anything else that is used for metabolic energy, is broken down into glucose, whose oxidation yields CO2 an H2O. One reason low carb intake helps lose weight is that, if the easiest molecules to oxidize aren't coming from the small intestine, then your system will turn to fat. If the low carb intake is part of ingesting fewer calories, then a calorie deficit from the incoming food will mean turning to fat deposits your body has stored.
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Re: Working on a Chain Gang

Postby Faradave on July 28th, 2016, 9:19 am 

As organic molecules, fats are based on chains of carbon. Those which are absorbed by digestion and not stored as your own fat or other structural elements (e.g. cell membranes) are metabolized by a series of chemical reactions which release energy for your body to do its work (primarily to maintain your body's temperature). The end product of the carbons is combination with oxygen you breath which is exhaled as carbon dioxide.

edit: What BiV said.
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Re: How does fat leave the body?

Postby Athena on July 28th, 2016, 11:27 am 

We don't actually lose fat cells. They can shrink like a sponge drying up, but they stay there to be refilled as soon as possible. Fat cells do die, but they are replaced.

How many fat cells you have depends largely on how many you gained during childhood. Adults can gain fat cells but not as fast as children. Good health really begins in childhood. Obese children gain a greater number of fat cells and they don't go away. They can only be emptied. This means it is much easier for them to regain lost weight, then the person who never had extra fats in the first place.

Losing weight is not just about reducing carbs, but also eating fiber and drinking plenty of water. If you are counting carbs, you can subtract the amount of fiber you eat from the number of carbs. Keep your system clean with carbs and water.

Some of us use food more efficiently than others. Do not fast to loose weight, because this only makes our body more efficient at sucking calories out everything we put in your mouth. Instead of fasting, begin every day with a breakfast to get your metabolism going.

Exercise is not just about burning calories, but also setting your metabolism to work efficiently. If you are sedentary, your metabolism gets sluggish and just doesn't burn calories fast. Aerobic exercise is best for having a more efficient, carb burning metabolism, and the more we exercise, the more we will want exercise. Yes, we can make our bodies crave exercise, just as we can make ourselves crave sugar, chocolate, alcohol, caffeine drinks.

Sugar-free caffeine drinks can help us lose weight, but they also take our calcium, so our use of caffeine should be limited.

If we can not jog or swim or climb mountains, fidget. Fidgeting can actually help us burn carbs. That is why nervous people tend to be skinny people. We might look a little strange sitting at a desk dancing in our chairs while a tune runs silently through our heads, but it could help us look better in our swim suits.
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Re: How does fat leave the body?

Postby BioWizard on July 28th, 2016, 11:39 am 

I haven't read everybody's posts yet, but I just wanted to point out that these two statements:

weakmagneto » 28 Jul 2016 12:39 am wrote:fat leaves the body by being burned off in the form of heat or energy.


weakmagneto wrote:we exhale most of it.


mean exactly the same thing in biochemical terms. "Burning off" fat or any carbon-based nutrient is basically oxidizing it sequentially until every carbon atom in it is combined with two oxygen atoms. That produces CO2, whose primary mode of elimination is through exhalation. A little bit of energy is released with every step (or few steps), and stored in high energy molecules (ATP, GTP, creatine phosphatse, etc) for use elsewhere.

In other words, fat is converted to both energy/heat and CO2.
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Re: How does fat leave the body?

Postby BioWizard on July 28th, 2016, 11:46 am 

From the article...

"None of this biochemistry is new, but for unknown reasons it seems nobody has thought of performing these calculations before," study authors Ruben Meerman and Andrew Brown of the University of New South Wales in Australia, said. "The quantities make perfect sense but we were surprised by the numbers that popped out."


Seriously? That's almost like saying "we just calculated the sum of angles a triangle, which for some unknown reason nobody has done before".
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Re: How does fat leave the body?

Postby Forest_Dump on July 28th, 2016, 2:59 pm 

When I first read this one it actually triggered an old memory of mine from when I was in 1st year biology and actually wondered the same kind of thing. Since I know neither "burning energy" or heat loss directly resulted in a loss of mass, I actually went through the exercise of trying to figure out where mass went when you lost weight. 1) I did learn in biology that mass entered the body through the digestive system and that actual experiments and/or records existed of comparing weight in vs. weight out. 2) Atoms and molecules are lost through the urine but apparently not enough to account for weight loss even taking into account 3) water lost through evaporation from the mouth, nose and skin (perspiration which includes salt). Other mass is lost through shedding skin cells (enough to double the weight of your mattress over time according to some studies) as well as hair loss (which is why I avoid the mirror more now) and shaving. So that did leave the (obviously reasonable and even taken for granted) hypothesis of the carbon lost in respiration. But way back when I was rolling this around in my head I had to wonder just how you would go about empirically testing and verifying something like that. But I definitely liked to see what I call real science in trying to test and verify something that looked good on paper but was really not much beyond informed common sense (with all the dangers that go with that).

BioWizard wrote:That's almost like saying "we just calculated the sum of angles a triangle, which for some unknown reason nobody has done before".


A bit of a tangent, I suppose, but actually that is how it was done originally. Some time ago I had wondered just why and how a lot of math was invented which led to wondering about the role of seeming lone gun geniuses in history, the "Big Bang" in Greek math, etc., which of course included Pythagorean theory, etc. Turned out a lot of that was based on literally up to 700 - 800 years of careful observations going back to records kept by the Babylonians (but including the Egyptians) and poured over by countless forgotten scribes who gradually began to notice regularities which led to other regularities (including noticing that the angles of triangles did seem to add up to a common sum). So, in fact, it was literally centuries of careful measurements of land parcels that led to the origins of formulas, etc. in geometry.
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Re: How does fat leave the body?

Postby BioWizard on July 28th, 2016, 3:32 pm 

Hi Forest, my analogy was to someone saying that today.
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Re: How does fat leave the body?

Postby BioWizard on July 28th, 2016, 3:45 pm 

Point being that whatever they claim to be pioneering is largely classical biochemistry and exercise physiology.
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Re: How does fat leave the body?

Postby Forest_Dump on July 28th, 2016, 6:06 pm 

BioWizard wrote:Point being that whatever they claim to be pioneering is largely classical biochemistry and exercise physiology.


True enough. To me, however, I always like the old fashioned independent testing of these kinds of hypotheses, etc. I even found value, in the past, of some of the questioning of evolution that required even more field verification of fossils, independent verification through DNA studies, etc. Of course, O2 in CO2 out makes perfect sense (where did that C come from?) but it is nice to see it tackled and all tied together.

BioWizard wrote:Hi Forest, my analogy was to someone saying that today.


Again fair enough and I acknowledge somewhat of a tangent but to me it was an interesting and at least somewhat relevant anecdote about the old fashioned way of inventing math and science from on the ground observations.
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Re: How does fat leave the body?

Postby BioWizard on July 28th, 2016, 8:01 pm 

Sure, but again that's all been done long ago, and the "calculations" are mostly rehashing old stuff.
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Re: How does fat leave the body?

Postby Braininvat on July 28th, 2016, 10:11 pm 

The answer to the forum title is "liposuction" isn't it?
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Re: How does fat leave the body?

Postby doogles on July 29th, 2016, 2:56 am 

Biowizard explained the broad biochemistry of it; Athena had a good point about being a wriggler or fidgeter if you wish to stay toned-up while burning some energy. and although it’s slightly off topic, I particularly liked this part of your post Forest_Dump – “Some time ago I had wondered just why and how a lot of math was invented which led to wondering about the role of seeming lone gun geniuses in history, the "Big Bang" in Greek math, etc., which of course included Pythagorean theory, etc. Turned out a lot of that was based on literally up to 700 - 800 years of careful observations going back to records kept by the Babylonians (but including the Egyptians) and poured over by countless forgotten scribes who gradually began to notice regularities which led to other regularities (including noticing that the angles of triangles did seem to add up to a common sum). So, in fact, it was literally centuries of careful measurements of land parcels that led to the origins of formulas, etc. in geometry.”

weakmagneto, getting back on track, you added – “Even if one traces the fates of all the atoms in the body, the secret to weight loss remains the same: In order to lose weight, one needs to either eat less carbon or exercise more to remove extra carbon from the body. “

If a weight loss discussion is part of the purpose of this post, an interesting point to bear in mind is that, when we take less food into our bodies in the sense of going into negative carbon or energy balance, without exercising simultaneously, our fat deposits do not disappear at first. The first to go is our 1% energy store in the form of glycogen. The next 14% of energy loss comes from muscle catabolism via the alanine cycle.

We lose muscle before fat.

This has been known for many decades in studies of convalescents recovering from injuries or surgery. As a personal example, I lost 10 kg weight in 8 days twelve years ago, following bilateral knee replacements. I looked as if I was about 100 years old with sagging skin, but most of my fat bulges remained.

In order to maintain muscle mass while catabolising fat, we have to exercise our muscles whilst dieting, otherwise we change shape like a convalescing patient. And if you expect to lose weight by exercising alone, keep in mind a ball-park figure of having to walk about four kilometres to lose about 150 Cal, and that you need to burn off approximately 5000 Cal for each kilogram of body-mass loss.
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Re: Concentrating on Conservation

Postby Faradave on July 29th, 2016, 10:12 am 

doogles wrote:...the sense of going into negative carbon or energy balance,

Your comment illustrates a nice fact about exact conservation laws, such as Conservation of mass-energy. Barring exchange* between its components, it can be broken into separate, very useful approximate conservation laws, (here, Conservation of mass & Conservation of energy). A chemical equation can be balanced correctly using either.

A chemist might carefully track the masses of reactants and products, essentially balancing the atoms on each side of the equation.

A physicist might prefer to track the energies of molecular bonds and the environment, likewise getting a correct chemical equation.

Using both however, allows a practitioner to predict the equilibrium concentrations of all the components from the initial conditions. One might, for example wish to predict the final alcohol concentration to be expected by fermentation of carbohydrate solutions under various conditions.


*In this case, phenomena invoking E = mc2 (fission, fusion, annihilation, creation).
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Re: How does fat leave the body?

Postby Athena on July 29th, 2016, 10:54 am 

Braininvat » July 28th, 2016, 8:11 pm wrote:The answer to the forum title is "liposuction" isn't it?


Now that is a good answer. That is the only way enough fat cells to make a difference are going to leave the body.

Doogles information is really good. Fasting is not the best answer to weight loss.

In order to maintain muscle mass while catabolising fat, we have to exercise our muscles whilst dieting, otherwise we change shape like a convalescing patient. And if you expect to lose weight by exercising alone, keep in mind a ball-park figure of having to walk about four kilometres to lose about 150 Cal, and that you need to burn off approximately 5000 Cal for each kilogram of body-mass loss.
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