A new US study reveals a surprising way that sites such as Instagram and Pinterest can ruin your meal: looking at too many photos of food can make eating less enjoyable, researchers said.

Researchers from Brigham Young University in Utah claim that a friend's obsession with posting meals on Instagram or Pinterest can spoil your appetite "by making you feel like you've already experienced eating that food," the researchers wrote.

"In a way, you're becoming tired of that taste without even eating the food," said study coauthor and marketing professor Ryan Elder. "It's sensory boredom -- you've kind of moved on. You don't want that taste experience anymore."

The researchers recruited 232 subjects to view and rate photographs of food. In one experiment, half of the participants viewed 60 pictures of sweet treats, such as cake and chocolates, while the other half looked at 60 pictures of salty snacks, such as chips, pretzels, and fries. After rating each picture based on how appetizing that food appeared, participants finished the experiment by eating peanuts and then rating how much they enjoyed the snack.

Subjects who had viewed the salty foods ended up enjoying the peanuts less, even though they had never looked at photos of peanuts, just at other salty foods, while the same effect didn't occur among those who had viewed the images of sweets.

"If you want to enjoy your food consumption experience, avoid looking at too many pictures of food," said coauthor Jeff Larson, also a marketing professor. "Even I felt a little sick to my stomach during the study after looking at all the sweet pictures we had."

Then again, Larson adds that if you have a weakness for a certain unhealthy food and want to prevent yourself from eating too much of it, you may want to look at more pictures of that food.

"You do have to look at a decent number of pictures to get these effects," Elder added. "It's not like if you look at something two or three times you'll get that satiated effect."

Their findings, announced October 3, are published in the Journal of Consumer Psychology.