The Physics of Gluttony; A physicist looks at obesity and weightloss

LiquidHAL wrote:
|| http://www.technologyreview.com/articles/04/11/wo_muller111204.asp?trk=nl
||
|| some exerpts:
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|| When you digest food, its carbon atoms enter your blood. Unless they
|| are expelled from your body, they add to your weight. But here is the
|| salient observation: the only effective way your body has to get rid
|| of digested carbon is to combine it with oxygen to form carbon
|| dioxide, and then expel it through your lungs. Unless you breathe out
|| the carbon, you gain weight.
||
|| The mistake people make is to think that an hour of moderate exercise
|| will change their body chemistry enough so that they'll "burn" away
|| the calories even when they are inactive. But unless you breathe more
|| rapidly, the carbon will stay in your body. If you want to lose
|| weight, eat less or breathe more. And the only effective way to
|| breathe more is through increased activity. There is no such thing as
|| stimulating your body into a higher resting metabolic rate.
||
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||
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|| He takes an extremely reductionist view of the subject, something i'm
|| sure most people here would strongly disagree with. Put I never
|| thought about it that way. Your cells break down glucose in a long
|| string of reactions, eventually getting CO2 and energy in the form of
|| ATP. Fats are broken down into components that are not glucose, but
|| they are added to the process in the middle, a step where glucose is
|| broken down into the same product.
||
|| So when you exercise, it's not purely the energy you expend that
|| loses weight. It's the carbon molecules from the foods you ate and
|| from
|| your fat leaving your body as CO2 where the weight is lost. This
|| view of weightloss ignores fat and carbs and instead focuses on
|| calories.
||
|| I've been on and off a low-carb diet for a while, but from what I've
|| read, it's beginning to seem like the low-carb aspect of the diet is
|| not what helps lose the weight directly. Reduced apetite, which
|| seems to be more from high protein rather than low carb, and strict
|| regiment that is easy to follow and keep up with, all seem to point
|| to calories as the major factor in losing weight, with the low-carb
|| part helping keep calrorie intake down.

You're wrong. It's not from the high protein, because on LC diets protein
is not guaranteed to be high. However, the carbs are controlled, and that's
what results in reduced appetite and less eating. So, it is really a direct
result from reducing carbs that weight is lost. Reduce carbs, eat less, lose
weight.

If you ask me, worrying about molecules lost is silly. You can't lose
weight by simply breathing in and out. You need to exercise to help create
a calorie deficit.

LiquidHAL said:

http://www.technologyreview.com/articles/04/11/wo_muller111204.asp?trk=nl

This is a good lunchtime article.... it is stocked with baloney.

Quoted message said:

Let me address this issue by invoking another physics

Quoted message said:

principle: conservation of mass. More specifically,
let me talk about the conservation of carbon atoms.
When you digest food, its carbon atoms enter your blood.
Unless they are expelled from your body, they add to your
weight. But here is the salient observation: the only
effective way your body has to get rid of digested
carbon is to combine it with oxygen to form carbon
dioxide, and then expel it through your lungs.
Unless you breathe out the carbon, you gain weight.

"Digest Food" is a key phrase. It may be misused here in the article.

A great physicist can be a miserable physiologist and screw up the
intrepretation of quite complex organic chemistry reactions that
represent real body functions.

For example, there are lactose sugar intolerant individuals and these
folks do not have the enzyme needed to digest lactose sugar. It passes
out of the body..... perhaps sometimes messily. There is carbon in that
there sugar.

These carbon atoms are ingested, and not digested, and are excreted from
the body, not exhaled.

Alcohol sugars and similar fake sugars can have similar effects on SOME
people, not all people. Carbon is ingested, but not exhaled and not
retained.

I know one lady who underwent bariatric surgery with a stomach reduction
and small intestine shortening.

She complained about only being able to eat a little, but she got used
to that.

What she couldn't get used to were enormous bowel movements even though
she had only eaten a small amount of food. She was losing weight at
nearly 1/2 pound per day for quite some time. Of course she had a total
of nearly 300 pounds that she could lose and still leave a real person
there.

Yes, she belched and had gas problemss as well.

So, it seems as if the "MASS BALANCE" type of argument needs to be
total, not just restricted to carbon exhaled.

That attempts to reduce a complex chemical behavior down to something
more like mere burning of charcoal.

The chemistry of food digestion is sufficiently complex that it would be
unwise to assume that all humans are alike. Even automobiles have
different efficiencies in burning gasoline, and humans are considerably
more complex biochemical machines than automobiles.

There are lousy spark plugs that can ruin your mileage in a car.

There are lousy enzymes that can ruin your fuel efficiency in human beings.

The ability to partly "PASS" ingested food, without uptake of it by the
body, is one of the aspects of people having different responses to the
same amount and kind of food. There is carbon in that "passed food".

The experience of "MASS IMBALANCE" wherein some individuals, such as
following bariatric surgery, to apparently excrete more solid mass than
ingested would invalidate the simpleminded "Mass Bala;nce" described by
the physicist.

Remember, a great physicist can be a miserable physiologist and screw up
the intrepretation of quite complex organic chemistry reactions that
represent real body functions.