Marketing researchers at Brigham Young University found that as people were repeatedly shown pictures of food, they became more satiated and less interested in eating the same kind of foods. Turns out, looking at your friend's food-centric Instagram feed (or the like) can spoil your appetite "by making you feel like you've already experienced eating that food," according to the researchers.
"In a way, you're becoming tired of that taste without even eating the food," said Ryan Elder, one of the study's co-authors. "It's sensory boredom -- you've kind of moved on. You don't want that taste experience anymore."
In the study, 232 subjects looked at pictures of common food items. Half the group was shown only pictures of sweets (such as cookies and chocolates), while the other half was shown only pictures of salty foods (such as chips and pretzels). Afterward, both groups were given salted peanuts as a snack and asked to rate how much they enjoyed the snack.
The group that viewed the salty foods was found to enjoy the peanuts less, even though the participants never looked at pictures of peanuts. In their minds (and their stomachs), they had already consumed all the salt they could handle."