Much is known about the scale of the obesity epidemic, but how much do we really know about the factors that contribute to obesity at an individual level? Researchers working from the Northern Ireland Centre for Food and Health and the Sport and Exercise Science Research Institute asked this very question. To answer it, they used eye-tracking technology to measure the gaze of people who were presented with sets of food images. This data was then used to assess if people who are obese or overweight responded differently to visual food stimulation compared with people who had a normal-weight body mass index.
Participants in this study completed the test twice – once in a fasted state, and again in a fed state (which involved consuming a liquid meal to self-reported fullness, and waiting twenty minutes). Each test was completed at least 5 days apart. The first stage was to complete a visual analogue scale questionnaire, to determine self-reported levels of hunger and fullness.
The second stage involved a series of visual probe tasks. This was presented as a set of food images – a mixture of low energy density (such as fruit and vegetables) and high energy density foods (such as chocolate and pizza). Food images were juxtaposed with control images such as stationary and tools. The images were displayed to participants and eye movement data was collected, assessing if the eye was drawn to particular images more than others during the task.
Results were analysis according to weight status of the participants, their gender, as well as considering whether participants were in a fed or fasted state during the visual probe task.
All participants paid greater attention to the high energy density food images, indicating that these types of food may be more instinctively attractive to people. One possible explanation may be that this response occurs because the brain is stimulated by foods which are higher in fat and sugar.
The results also found that:
Men who werepaid more attention to high energy density foods than men with a body mass index in the normal range.
There was no difference in results across the fed or fasted conditions. Women who were overweight paid more attention to the lower energy density food images.
Other researchers have hypothesised that overweight women may have developed additional strategies to divert their attention from higher energy density food.
As aprofessional, this type of research has the potential to help better understand where and how people direct their attention (otherwise known as attention bias) in relation to food. Since attention bias is a potentially modifiable factor, further research in this area is needed to determine what techniques might help modify a person’s response when presented with high energy density foods.