Eating while doing something perceptually demanding makes it harder to notice that you're feeling full, according to new research from the University of Sussex. Professor Martin Yeomans, Dr Sophie Forster and colleagues found that when your senses are engaged in an engaging task, you are less likely to adjust how much extra food or drink you consume. The team tested 120 participants, feeding them lower and higher calorie drinks and tasks that required both little and a lot of attention.
The team found that participants who were fully engaged in a perceptually demanding task ate about the same amount of chips regardless of whether they were initially given a high-calorie or low-calorie drink. But the people engaged in a task that required less of them could adjust how much of the extra snack they ate. The people in this group ate 45% fewer chips after the higher energy drink than after the lower energy drink.
Previous research has shown that when perceptual demand is high – so that's where the senses are fully involved – the brain filters out some of the sensory information. This is the first time research has shown that sensory and nutrients associated with fullness (satiety) can be filtered out in a similar way.
Professor Martin Yeomans of the School of Psychology at the University of Sussex said:
“Our study suggests that if you eat or drink while your attention is distracted by a highly engaging task, you are less likely to see how full you feel. You're more likely to continue snacking than if you had eaten while doing something less engaging. This is important for anyone who wants to stay healthy:if you're a regular TV-watching snacker, and you're watching a compelling thriller or mystery, or a movie with a lot of audio or visual effects - you probably don't notice when you see a feel full. Video gamers and crossword puzzle players should also pay attention!
“We already knew that feeling full can be influenced by the texture and appearance of food, as well as by 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 that moment.”
About the study
One hundred and twenty participants drank either a low-saturation drink (75 kcal) or a high-saturation drink (272 kcal and thicker texture), while simultaneously completing a task that was either low or high in perceptual question. The participants who were given the low perceptual load task and given the saturated drink felt fuller and ate 45% less of the snack they were given afterward. However, the participants given the task of perceiving the higher load could see less when they felt full and ate more of the snacks offered. The researchers conclude that a person's ability to notice when the body feels full depends on the amount of available attention 'remaining' in the brain.
The results provide the first evidence that attentional theory (the idea that a person has a limited amount of sensory information that they can notice) can be successfully applied to eating habits.
