This is why your phone is making you gain weight

Like peanut butter and jelly or bacon and eggs, snacking while lounging around and watching television is a natural pairing. Of course, by the time the credits roll on that episode of Game of Thrones or The Sopranos, people are often surprised by how much they ended up eating while watching TV.

Researchers from the University of Sussex set out to answer why people overeat so frequently while watching television, or for that matter while playing video games or scrolling on their smartphone. They discovered that when a person eats while enjoying “perceptually demanding” content, it’s that much harder for their brain and body to recognize that they’re full. 

Television shows and smartphone apps are designed to captivate the senses and monopolize our attention spans. Consequently, when we combine these sources of entertainment with food, our bodies have a much harder time recognizing that we’ve hit our calorie limit. 

“Our study suggests that if you’re eating or drinking while your attention is distracted by a highly engaging task, you’re less likely to be able to tell how full you feel. You’re more likely to keep snacking than if you’d been eating while doing something less engaging,” explains study co-author Martin Yeomans, a professor from the School of Psychology at the University of Sussex, in a release

“This is important for anyone wanting to stay a healthy weight: if you’re a habitual TV-watching snacker – watching, say, an engaging thriller or mystery, or a film with a lot of audio or visual effects – you’re not likely to notice when you feel full. Video-gamers and crossword solvers should also take note!” Professor Yeomans adds.

In all, 120 people took part in the experimental portion of this study. Each participant was given either a high-calorie or a low-calorie beverage and then told to complete a task. Half of the participants were given a task requiring their full attention, while the other half were provided with a less demanding challenge. Then, after all the tasks were done, participants were offered some potato chips.

Subjects who had to complete a more perceptually demanding task generally ate the same amount of chips, regardless of whether they had drunk the high or low-calorie beverage. Participants who had to complete a less perceptually demanding task, however, ate 45% fewer chips after the higher calorie drink in comparison to after the lower-calorie beverage.

These results indicate that the people who were given a task that took up all or most of their attention were unable to tell when they felt full. This suggests, according to the study’s authors, that our brains only have a set amount of “attention” we can use at any given moment, and that includes stomach sensitivity. Prior research has already established that when the human brain is focusing on a task that requires maximum perceptual attention, it can sometimes block out certain stimuli it deems unnecessary. 

This is the first time, though, that a connection between this neural tendency and eating has been uncovered. It seems that when we’re focused on a good TV show or something happening online, our brains often decide that whatever is going on with our stomachs just isn’t as important and can wait.

“We already knew that feeling full could be affected by the texture and appearance of food, as well as pre-existing expectations about how full we think a type of food should make us feel. Now we also know that feeling full depends on how much sensory information our brains are processing at the time,” professor Yeomans concludes.

The full study can be found here, published in Appetite.