system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If I eat a bag of 500g potato chips, will my weight gain be definately more or less than 500g?

Let's assume I've used up all the calories I've taken in today, then I eat this bag of 500g chips, will my weight gain be definately more or less than this 500g?

My instinct tells me that it'll be less than 500g because the human body can't absorb everything that's in it, am I right? Or are there gonna be some more complicated chain reactions that's gonna happen?

EDIT: Based on most of the answers, it seems gaining weight is a bit harder than I think. But I feel I gain weight easily if I don't watch my diet. Maybe I easily and constantly eat junks all the time when I'm not careful lol.
gpt
For the sake of simplicity let's say you are able to eat the chips in a single bite. In that instant you will increase in mass by 500g. 

As soon as you eat them you will begin losing weight because you're breathing contains water and other gases, each breath makes you lighter.

You begin to digest the chips which takes energy, and breathing, heart beat, maintaining temp etc. also takes energy, so some of the calories will be used in these processes. Unused absorbed calories  (if there are any) will end up being stored as fat.

At some point you will excrete the undigestable components of the chips along with a portion of your gut bacteria which will also reduce your mass.