What happens when an average male (25-35 year old, no health issues) with a TDEE of ~3000 has an ‘Epic Cheat Day’ and eats 10,000 calories? Are all the surplus 7,000 calories fully coverted to body weight? Or does excess food get excreted without digestion? Or does the thermic effect go up a lot and you don’t actually add weight equivalent to +7000 calories?
The majority gets stored as energy , provided there isn’t any vomiting or diarrhea.
People different in adaptive responses to energy surplus, e.g. there are obesity-resistant and sensitive folks, but the body is really good at storing energy.
The thermic effect of food is proportional to energy intake so yes, technically it goes up when intake goes up.