What do you imagine a doctor would do with this information?

Most likely, they'll say hmmm, that's strange and you probably should try to avoid eating so much peanut butter in one sitting. Maybe they'll give you an invasive test that's probably not conclusive or inexepensive.

Plenty of other foods fill me up just fine. A 4oz steak and some broccoli. Bacon and eggs. Meat + a veg does me fine.

> See a doctor.

Doctors know next to nothing about gut biome stuff.

"I don't get full eating an entire jar of peanut butter" is going to result in the doctor telling me to not eat a jar of peanut butter.

Heck plenty of people don't get full eating entire tubs of ice cream. The answer is to avoid downing tubs of ice cream.

Eh, different people respond to food differently. This is not controversial. This whole discussion has a huge amount of bro science, and very little actual science. To the limited extent such a thing even exists in the nutritional space.