If I ate a 3500 calorie meal but then nothing else, would I still gain a pound of weight over time, though? I guess I'm just wondering how a pound of anything can spring forth from a situation where less than a pound of something is ingested. I understand it's energy and that just because you eat a 3 pound meal doesn't mean you'll gain 3 pounds, but I guess it's hard for me to wrap my head around a measurable weight manifesting from something that's less than that (again, speaking purely hypothetically and trying not to take into account the fact that people would still be imbibing other meals and whatnot).
Like, I know that if I take a 1 pound rock and do anything to it, there'll still be 1 pound of rock regardless of if I need to include the dust that's now in the air from smashing it, or whatever soot I get from blasting it with water. Is this the same with food and calories? In a vacuum, can .5 pounds of 3500 calorie food still cause me to gain 1 pound of fat?
Well, the caloric value of food varies.
Fat has about 9 calories per gram.
Protein, alcohol, and carbs about 4 calories per gram.
This despite the fact that they're the same weight/mass.
(Excuse me if I'm slightly off on the numbers, this is straight from nutritional memory.)
If you eat 3500 calories in one meal, you have doubled the daily caloric resting needs for an average human of around 6 foot height and around 180 pounds sorry for imperial units. However, that is still only an EXCESS of somewhere from 1500-1800 calories, see? You used the rest in living and breathing even while sitting around. If you exercised a lot this day, it might not even be an excess.
But, if you spend the rest of the week at exact maintenance, and if the body reserves the entire excess in storage rather than letting some of it go through the evacuation process (both are variable and spoken of in averages for humans), then yes in that week you might vary your weight by .3 to .5 pound, although your actual weekly weight will vary more by water weight because there's a lot of systems interconnecting here.