Nutrition Question

[toddjh]

Jermey, Zakur, I am afraid that both of you are wrong; there is no violation of the conservation of energy.

If you eat one kilogram (including water), but your body ends up weighing 1.1 kilograms more, there certainly is.

The energy from food comes from the chemical bonding energy that is released when the food is metalbolized. The food had to absorb energy in order to be produced, then there was energy that was expended in order to manufacture, pack, and distribute, and sell the said food. By contrast, you have to expend energy to obtain, eat and digest the said food, which ultimately leads to the food providing some of the energy that is needed to support your life processes (for a while, at least).

Yes. But this has nothing to do with how the mass of food can somehow increase when you eat it.

Now then, does a 1700 pound airplane violate the conservation of energy when 144 pounds of fuel is used to provide the energy needed to fly thousands of feet above the ground for three hours?

No, because the mass of the exhaust from the engine is equal to the mass of the fuel that's expended. Just as the mass of the food you eat is equal to the mass your body stores as fat plus the mass of the waste you excrete.

No, of course not! And why? Because there is a great deal of energy that can be obtained by breaking the chemical bonds in the fuel. By the same token, with the right food, there is also a great deal of energy that can be liberated via biological processes (as opposed to mechanical) in those chemical bonds.

Yes. But I'm still unclear how you think this manages to create mass.

Jeremy

 

[Crossbow]

But, the plane gets lighter as it burns the fuel, not heavier. Or, am I missing something?

-TT

So what if the plane gets lighter as fuel is burned? Many military aircraft have in-flight refueling capabilty.

And besides, the same sort of thing happens with animals. As they do work without taking in food, they get lighter as well.

Special Case: unless one is doing rather light work and that one has just ate some high energy food and started the work before the food had been fully metabolized, then it may be possible for one to actually gain weight while working. In any case however, there is no violation matter and energy conservation laws.

 

[rwald]

How could that special case work? I still don't see how the food's mass could increase as a result of being metabolized. I mean, I know that with relativity you can turn energy into mass, but I don't think that breaking and making chemical bonds is going to have much effect on the mass. At least, it won't increase the mass.

 

[Crossbow]

Look people, this should be a reasonable concept to grasp.

The average adult human doing an average amount of activity needs approximately 1800 calories per day just to maintain their weight.

If the activity level remains constant, but more than 1800s calories are ingested, then ones weight will increase.
If the activity level remains constant, but less than 1800s calories are ingested, then ones weight will decrease.
If the activity level increases, but the caloric intake remains constant, then ones weight will decrease.
If the activity level decreases, but the caloric intake remains constant, then ones weight will increase.

OK so far?

If so, then here is another number: body fat has about 3500 calories/pound.

So, if an average adult is doing an average amount of activity were to eat one pound of a super high calorie food product that has 5300 calories/pound during a one day time period, then he will put on one pound of fat (5300 = 1800 + 3500).

All right, how is that?

 

[rwald]

Fair enough. If he eats one pound of food, than I would expect that he could gain weight up to and including a pound. The question is whether it's possible for less than a pound of food to have 3500 calories. If that's the case, than we have issues.

 

[toddjh]

Fair enough. If he eats one pound of food, than I would expect that he could gain weight up to and including a pound. The question is whether it's possible for less than a pound of food to have 3500 calories. If that's the case, than we have issues.

It is possible, and no, it doesn't cause problems. Substances that contain more than 3500 calories a pound have to be broken down in order to be converted to fat. There also have to be sufficient raw materials to construct the fat from. Your body will take whatever energy and raw materials are available, and excrete the rest.

Calories are a fairly abstracted measure of chemical energy; just because a pound of fat contains 3500 calories doesn't mean that anything that contains 3500 calories can be converted into a pound of fat. That's like saying that a gallon of gasoline can power a lawnmower for 12 hours, so anything that can power a lawnmower for 12 hours can be converted into a gallon of gas.

Jeremy

 

[toddjh]

All right, how is that?

Fine, up until the very end. Just because it takes 3500 calories to burn a pound of fat doesn't mean that it takes exactly 3500 calories to make a pound of fat.

The 3500 calories per pound figure is a rule of thumb used by nutritionists for people trying to lose weight, not an equation for biochemists.

Jeremy

 

[rwald]

I guess it sort of makes sense from a conservation-of-energy point of view, but how can it make sense from a conservation-of-mass point of view? I mean, if the system "human + food that is more than 3500 calories per pound" weighs x total pounds before the person eats the food, how can it weight more than x pounds after the person eats the food?

 

[Crossbow]

Fair enough. If he eats one pound of food, than I would expect that he could gain weight up to and including a pound. The question is whether it's possible for less than a pound of food to have 3500 calories. If that's the case, than we have issues.

Whew! Thanks much, I was beginning to wonder if I could ever explain this stuff.

Sunflower oil is edible and has about 4000 calories per pound, so I imagine that one could drink it and put on weight rather quickly.

Although, I would prefer a combination of pizza, root beer, and a Doctor Who marathon, while not as fast, it would be much more enjoyable.

 

[Crossbow]

Fine, up until the very end. Just because it takes 3500 calories to burn a pound of fat doesn't mean that it takes exactly 3500 calories to make a pound of fat.

The 3500 calories per pound figure is a rule of thumb used by nutritionists for people trying to lose weight, not an equation for biochemists.

Jeremy

Exactly right. That is why I laced my post with terms like 'average adult', and 'average amount of activity', and so on. Strictly speaking, one should do an analysis on the subject in question to determine just how many calories they need and how many the expend during certian activities in order to accurately determine just what should be done.

However, this sort of data can be impractical to obtain, so usually a doctor's visit is reccomended prior to starting a diet and/or exercise program.

 

[toddjh]

Exactly right. That is why I laced my post with terms like 'average adult', and 'average amount of activity', and so on. Strictly speaking, one should do an analysis on the subject in question to determine just how many calories they need and how many the expend during certian activities in order to accurately determine just what should be done.

However, this sort of data can be impractical to obtain, so usually a doctor's visit is reccomended prior to starting a diet and/or exercise program.

Okay, you're kind of losing the thread here. The debate is whether you can gain more weight from eating than the food actually weighs.

The fallacy in your argument is one of assuming that it is a zero-sum game. In other words, you are assuming that since

1 lb. of fat -> 3500 calories of energy, then
3500 calories of energy -> 1 lb. of fat,

which is simply not the case. It's the same as saying that, since 1 ton of TNT can produce 4.2×10⁹ joules, you can use 4.2×10⁹ joules to produce a ton of TNT.

You said yourself in another post that sunflower oil contains 4000 calories a pound, which, by your logic, should produce about 1.14 pounds of fat. You really don't see a problem with transforming 1 pound into 1.14 pounds? You don't see how that is a violation of conservation of energy?

Jeremy

 

[jj]

Re: Re: Re: Re: Re: Re: Re: Nutrition Question

O₂ in and CO₂ out.
Sounds like a net loss to me.

Not that simple. O2 gets fixed into other things, too.

 

[BillyJoe]

Re: Re: Re: Re: Re: Re: Re: Re: Nutrition Question

jj,

This must mean that are more molecules of O₂ going in through the lungs than molecules of CO₂ going out through the lungs.
Is that right?

bj

 

[Crossbow]

Okay, you're kind of losing the thread here. The debate is whether you can gain more weight from eating than the food actually weighs.

The fallacy in your argument is one of assuming that it is a zero-sum game. In other words, you are assuming that since

1 lb. of fat -> 3500 calories of energy, then
3500 calories of energy -> 1 lb. of fat,

which is simply not the case. It's the same as saying that, since 1 ton of TNT can produce 4.2×10⁹ joules, you can use 4.2×10⁹ joules to produce a ton of TNT.

You said yourself in another post that sunflower oil contains 4000 calories a pound, which, by your logic, should produce about 1.14 pounds of fat. You really don't see a problem with transforming 1 pound into 1.14 pounds? You don't see how that is a violation of conservation of energy?

Jeremy

You bring up some good points Jeremy, so me let see if I can break it down.

As for the TNT, making a ton of would be a rather energy intensive process (to say the least!), so I would say that it would take at least 4.28 billion joules to make a ton of it.

As for fat production, perhaps I should point out something that you may not be aware of, and that is the body already has fat cells, and when one puts on weight, more of these cells are not created, rather the exisiting fat cells increase in size.

As for the sunflower oil, I think that I need to reiterate (this makes the third time for those of you keeping track) that the average adult needs about 1800 calories every day just to maintain its current weight, so expected weight gain would be something like 0.6 pounds ((4000 cal -1800 cal)/3500 cal/lb = 0.6 lb).

So no, I do not see a violation of the conservation laws.

 

[Jaggy Bunnet]

But the question is whether the weight gain could be MORE than the weight of food intake. As the question is theoretical, why not simplify it by ignoring production of waste and utilisation of energy?

Consider a set of scales. On each end is an identical person and a bottle containing one pound of olive oil. The scales are in balance. Neither person does any work at all (or both do equal work/burn equal calories) nor produces any waste and nothing is added to or removed from either end of the scales.

If one person drinks the olive oil, does their side of the scale increase in weight compared to the other side?

If so, then consider the following. A man climbs a ladder carrying a bottle of olive oil. For the purposes of the thought experiment, the work done is perfectly converted into potential energy, with no inefficiencies such as sound, heat etc. At the top of the ladder the potential energy is equal to the work required to lift the total weight through the height of the ladder. If the man now drinks the olive oil and the total weight increases, is there not additional potential energy? If so, where does this energy come from? I don't think it can come from the oil because, as I understand it, the 4000 calories in the oil would still be present in the 1.14 pounds of fat.

 

[Crossbow]

But the question is whether the weight gain could be MORE than the weight of food intake. As the question is theoretical, why not simplify it by ignoring production of waste and utilisation of energy?

...

Hold the phone! The start of this thread has a different question.

 

[toddjh]

Hold the phone! The start of this thread has a different question.

"She said that my thinking is not correct and that you can effectively gain more weight than the weight of the food you eat, depending on the food's calorie level."

That's the phrase in the original post that most of us were talking about, I think.

Jeremy

 

[Jaggy Bunnet]

Hold the phone! The start of this thread has a different question.

It does? What question is that?

 

[Jethro]

Hold the phone! The start of this thread has a different question.

The wife & I were discussing food intake & weight gain - I suggested that no matter what you eat, the most weight you can gain is equal to the weight of the food you eat. For example, If you eat a pound of Doritos, the most weight you will gain is a pound.

Read->Comprehend->Post

 

[toddjh]

As for the TNT, making a ton of would be a rather energy intensive process (to say the least!), so I would say that it would take at least 4.28 billion joules to make a ton of it.

But that's a naive viewpoint. If you don't possess the chemical building blocks of TNT (say, if you don't have any nitrogen), then no amount of energy is going to be sufficient (ignoring nucleosynthesis and the like). Likewise, no matter how many calories a type of food contains, if it doesn't possess the exact proportion of materials necessary to create fat, not all of it is going to be stored in the body.

As for fat production, perhaps I should point out something that you may not be aware of, and that is the body already has fat cells, and when one puts on weight, more of these cells are not created, rather the exisiting fat cells increase in size.

Of course, but the content of the fat cells still has to come from somewhere. The only relevant factor is the mass of the fat, not the number of cells.

As for the sunflower oil, I think that I need to reiterate (this makes the third time for those of you keeping track) that the average adult needs about 1800 calories every day just to maintain its current weight, so expected weight gain would be something like 0.6 pounds ((4000 cal -1800 cal)/3500 cal/lb = 0.6 lb).

Also irrelevant. You're still behaving as if you can create fat from thin air using only calories. As I've said (this is also the third time), 3500 calories is what you get from burning a pound of fat, not what it takes to create a pound of fat.

So no, I do not see a violation of the conservation laws.

So what happens if the person has already eaten their 1800 calories for the day, and then drinks a pound of sunflower oil?

Jeremy