My friend and I are having an argument. I say you can’t gain a pound from just eating or drinking something that weighs less a pound. She feels that if it has more 3500 hundred calories and weighs less than pound you will still gain a pound. First can something that has 3500 calories weigh less than pound? Can a person gain a pound from eating something that weighs less than a pound without taking in anything else like water?
This site says that if you eat 3500 food calories more than your body needs you will gain a pound. According to this site some pizzas contain about 4800 cal/lb.
So if you have eaten your daily minimum of about 2000 calories and then eat 11-3/4 oz. of one of those pizzas you’ll gain a pound
How is it possible that if I eas something that weighs less than a pound I will gain more than a pound? Isn’t that like saying if I pick up rock than weighs less than pound and break it apart and put it back together in another form I can make it weigh more than a pound?
The fat that results from the calories is more dense than the food containing the calories?
I’m not a nutritionist. All I know is what I read in the cited sites.
But then won’t the fat that results have to filled up with something else like water? Just because there is a greater volume of less dense material shouldn’t make it weigh more.
Does the pizza weigh less than a pound?
This is great! I’ve invented theme park that makes electricity! I’ll give everyone on the ferris wheel pizzas, and tell them only to eat them at the top. The extra weight will bring them down the other side, driving the generator for the strobe lights in the haunted mansion! 
No, by the basic physical principle of conservation of mass.
No. How could you? Calories and density have nothing to do with it, ultimately. You could get close, maybe with butter I guess. But your body can’t manufacture mass out of thin air. And if it did, carbon would count. I’ve heard that some foods cause you to “retain water”, but even then you’d have to take in more than a pound of water and that food to gain a pound.
Tell your friend, even if she’s cute, to use her branes. 
We’ve discussed this before, I think.
Could eating something that weighs less than pound cause a person to produce more cells that then fill with air “creating” more than pound of weight on that person?
No.
You know what poops is, right?
How about before you drop the kids off at the pool? Could you have greater than a pound gain with the ari brought in including the loss to heat?
You’re not gonna gain the weight from the air but from the water. Water has weight but no calories and that’s why you say to lose a pound of fat, you must reduce your intake by 3500 calories and not the 4086 calories in straight fat. (454 grams/lb times 9 calories/pound of fat) Good explanation.
So say you eat say pure lard in excess of what it takes for you to maintain you weight. At 9 calories per ounce, it’s only gonna take 389 grams or about 0.86 pounds to equal 3500 calories. But, in making that pound of fat, your body will have to retain some water in addition to the lard calories. (this is purely hypothetical, of course. In real life, it’s tough to make everything work out exactly.)
We’re assuming that the pound is put on as fat, from fat. Fat has 9 calories per gram. But what if those calories were used to build muscle, instead of fat? Muscle has (roughly) 2 calories per gram. Assuming we’re buillt about like pork. I can’t find a calorie content of human meat.
So, theoretically, if the energy used from a pound of lard (roughly 4077 calories) was used to create muscle tissue, wouldn’t it create 2039 grams of muscle tissue, or roughly 4 pounds?
Of course, you’d have to consume the building blocks of muscles (proteins and amino acids) from food other than your pound of lard. This could come from the baseline food you need simply to maintain your weight. The pound of lard is the extra pound of food which, when properly utilized as energy, makes you gain 4 pounds of muscle.
4 pounds from one pound is a lot. But what if it was half a pound of protein and half a pound of fat?
protein calories in 227 grams = 454
fat calories in 227 grams = 2043
So you’d have 2497 calories and 227 grams of amino acids with which to build muscle from this meal alone - not counting nutrients you’d consumed elsewhere in the day or amino acids that your body pulls from the blood to build muscle.
You can’t gain more than a pound from eating one pound of anything.
One pound of fat may have 4100 calories or so. But body weight is a mixture of water, fat, proteins, glycoproteins, etc. It also takes time and energy to digest food. Digestion, particularly when given a high load, is not 100% efficient. Some of the energy is also required to break bonds, other energy is lost as heat. When someone says “it takes 3500 calories to store one pound”, this is a rough and inexact figure that averages many factors. These factors don’t include steatorhea. The body does not violate basic chemical principles.
It seems reasonable to me that consuming less than a pound of food which is high in caloric value could prevent you from burning off/exreting a pound that you otherwise would have–in effect, making you gain more weight than that of the food under consideration.
Just a WAG.
Just suppose your daily minimum intake of food weighs 1 pound. Eating 1 pound of food you will stay at the same weight, neither gain nor lose weight. Your intake exactly matches the amount you burn.
So one day you eat 1 3/4 pounds of food. Your normal minimum amount plus an extra 3/4 pound. Could you gain 1 pound from the extra 3/4 pound you eat? My WAG - yes it’s possible. The extra pound comes from the whole 1 3/4 pounds, not just the extra 3/4 pounds.
Why does this seem so simple to me?
If you weigh 180lb, and then you eat a pound of lard and nothing else (from the op- “without taking in anything else like water?”), there’s no way you can then weigh more than 181lb. You would weigh exactly 181 for a short while, but that would be true if you ate a pound of lettuce. Calories are of no consequence at this point. And you would immediately begin to lose that weight due to water loss and such.
I had a woman argue with me once that if I had two slices of bread and two pats of butter, and I ate one slice plain then the other slice with both pats, I would gain more weight.
Where do people gat there ideas?
The body can’t create mass. It either keeps it, or passes it along. As poop and piss or sweat, mostly.
Don’t forget CO[sub]2[/sub]. We breathe out a lot of oxidized sugars in the form of carbon dioxide each day too.
Food with 3500 calories can only add a pound of fat if you add water into the mix. The water plus the calorie laden food (which weighs less than a pound) together weighs more than a pound.
If one doesn’t drink the extra water, then, in order for that calorie laden food to add a pound of fat, it will take water from other places in your body, thus, not actually increasing overall weight.
As others have said, the matter for the extra mass of one pound has to come from somewhere, and it must be conserved.
Peace.