Am I correct in saying that it is impossible to gain more weight than you consume?

[Fanghur]

I've been having this debate with my mom for ages now, and to be frank, she's really starting to annoy me, because her argument seems utterly vapid from a scientific point of view. I once made the common sense statement that it is not possible for a person to put on more weight than the net weight of their daily food consumption (in other words, if a person, ANY person, eats say 0.5 lbs of food in a single meal, the person can't gain more than 0.5 lbs as a direct result of only that 0.5 lbs of food consumed), and she keeps saying that I don't know what I'm talking about. To me this isn't even a topic worth debating, because it is a simple matter of conservation of mass, that extra weight would have to come from somewhere, it couldn't just come from nowhere.

 

Can someone please settle this debate once and for all, because it is getting very tiresome.

[zapatos]

There are 453.59 grams in a pound.

There are 9 calories per gram of fat.

It takes about 3500 calories to gain one pound of body fat.

 

If you ate one pound of fat, that would be 453.59 x 9 = 4082.31 calories.

 

That would seem to indicate that you can gain more that one pound of weight by eating one pound of food (made of pure fat).

 

I assume it is because we don't typically count water as food, and my guess would be that water gets incorporated into body fat.

 

I don't think it is possible to consume less than one pound of all substances combined (food and water) and still gain a full pound of body fat.

Edited September 24, 2012 by zapatos

[Fanghur]

Okay, allow me to clarify exactly what I mean. When I say 'gain weight', I'm not talking about the the weight of fat that results from eating. It may well be possible for a person to eat 0.5 pounds of food and put on more than that in body fat, but that extra weight in fat would, unless the laws of physics have changed, by definition be at the expense of an equal amount of weight in something else in the body. In other words, lets say a scale says a person weighs exactly 180 lbs right before a meal. The person then consumes 3 lbs of food and drink and then goes back onto the scale. The scale would now read 183 lbs.

 

Now, what I'm trying to convince my mom is that it is not physically possible for that person, assuming that they don't eat or drink ANYTHING else that day, to weigh themselves the next morning and find that the scale says they now weigh, say, 185 lbs, or even still 183 lbs. Because as far as I can tell this is a closed system, and that extra 2 lbs of mass would by definition have to come from some external source, otherwise it would effectively be creating mass from nothing, which the laws of physics forbids.

 

Now, in this particular set of conditions, am I right or wrong?

[zapatos]

Right.

[dmaiski]

you can say its all water weight (which is true)

also even if you don’t drink, water is produced in respiration, so if you weigh yourself before you have "dumped the waste products" so to speak you wont get an accurate measure

 

another thing, there’s an off chance your scale is broken, or miscalibrated

 

 

[swansont]

There are 453.59 grams in a pound.

There are 9 calories per gram of fat.

It takes about 3500 calories to gain one pound of body fat.

 

If you ate one pound of fat, that would be 453.59 x 9 = 4082.31 calories.

 

That would seem to indicate that you can gain more that one pound of weight by eating one pound of food (made of pure fat).

 

I assume it is because we don't typically count water as food, and my guess would be that water gets incorporated into body fat.

I noticed that some time ago and came to the same conclusion.

 

I don't think it is possible to consume less than one pound of all substances combined (food and water) and still gain a full pound of body fat.

For animals, no. But that's because, unlike plants, we exhale CO2 rather than taking it in. Plants get much of their mass from the air, while we shed some ours that way.

[Ophiolite]

Could you ask your mother where she thinks this extra weight is coming from?

 

And, if I may be indelicate, is it possible your mother is a little on the heavy side and seeks to avoid personal responsibility for this situation.

[Fanghur]

Could you ask your mother where she thinks this extra weight is coming from?

 

And, if I may be indelicate, is it possible your mother is a little on the heavy side and seeks to avoid personal responsibility for this situation.

 

To be honest, I suspect that she just isn't properly thinking about what she said; either that or we're thinking of two different situations. And no, she's not. At least no more so than most women in their 50s.

[John Cuthber]

In the ordinary way of things on a science website, there's no way your mother could be right.

 

However, after a few hash brownies and a case of "the munchies" she may have a point.

[Derin]

Humans only use the things that enter our digestive tracts as a source of matter (barring obvious exceptions like intravenous feeding), so assuming you're counting water in your food weight, you're correct. In fact, humans breathe out some of what we consume (the carbon part of CO2), so even if you don't take into account perspiration, obvious forms of waste elimination and the negligible amount of mass lost through energy use, it's still impossible to weigh as much as is taken in in the long run.

[jasekiwi]

unless your mother is capable of transforming energy in to mass..............

[Jens]

Back to the initial question.

Of course as the others have stated for all practical means the answer is a clear no.

Even if you eat pure fat, you are not gaining this amount of weight (since you need to burn other materials to pay for the energy of digestion and transformation into human fat with the correct fatty acid composition).

The answer is only yes, if you consider drinking softdrinks or beer not as consumption (But that is a bad definition of consumption of course).

 

A more detailed biochemical consideration:

 

Considering mass:

The human body has the following input:

- liquid food (mainly water)

- solid food

- Oxygen (There are actually a few reactions in which CO₂ is incorporated, but they can be ignored)

Output (roughly sorted by amount)

- Water loss through breathing and sweating (This is what boxers are using to loose some grams to get their fighting weight)

- urine (mainly water)

- excrements

- CO₂ loss through breathing

- Lost surface proteins (hairs are falling out every 8 years, dead skin, ...)

 

So if we consider liquid food and solid food as consumption, theoretically you can gain weight, if there is a food substance that is converted to a human substance by consumption of oxygen without immediatly releasing CO₂. However there is no such substance, because humans cannot convert fat (no matter if it is human body fat or eaten fat) into into carbohydrates (which have much more oxygen linked to the carbons). Some plants can (like the coconut palm).

 

And just consider you are eating and drinking easily about 2 kg and more a day. Gaining 2 kg per day means you are dead before half a year is over.

 

 

Considering energy / calories and ignoring water (the long term view):

Body weight before lunch and after lunch is much dependent on the amount of water you drink. However, at the end of the day (so to speak, even literally ) water does not count since all superflous water is quickly lost via the urine, it makes more sense to look at the energy value (or "calories"), since all usable energy which is more than the body consumes is eventually transformed into body fat as a reserve (unless you are a body builder and build up muscle protein). So the difference of the calories you take up (eat+drink) to the calories you burn gives a good hint of how many weight you can gain in form of fat, since the human metabolism can transform all major substances in the food (fat, sugars, proteins) into fat.

 

So now again assuming you eat 100g of pure pork fat (which is close to human fat). And we will not count for water input or output (since it has no long term effect). You wil not gain 100g in weight because:

- The time you need to eat and digest you already burned fat to CO₂ and H₂O, (because you cannot turn of your brain for example).

- The fat is hydrolized in the gut. The enzymes and the bile for this need to be produced. The enzymes are digested themselves and need to be reconstructed. This all leads to burning fat to CO₂ and H₂O. There is a loss in bile.

- Not all fat is resorbed (partially also due to some microorganisms in the gut)

- In the liver the components of the fat need to be reassembled again (again energy consumption, which equals to burning fat to CO₂ and H₂O.)

- all the fat needs to be transported and incorporated into the fat tissues.

 

So it is impossible to gain 100g of weight with 100g of fat. And I doubt that even when you do not count water you drink as input and still count the water in the fat tissue as weight (considering that body fat tissue roughly only has 70% of fat and the rest are water and proteins) you can gain more than 100g fat tissue out of 100g fat+proteins in food.

 

And a hint:

Avoid the fatty fast food. It is unhealthy mainly because for most individuals it has a bad relationship between calories and stopping hunger. This is why over time many indiviuals constantly gain weight. The human hunger regulation system is not tuned for this kind of food -- at least in many cases. And it is hard to fight against the hunger regulation. So from a subjective point of view people (your mother?) are right: They have the impression that they are gaining more weight than they are eating.

Edited November 1, 2012 by Jens