The stimulus piece

One of the cognitive theories of obesity is that people who are overweight or obese are more likely to notice and be distracted by food.  This is known as an attentional bias. To test the role of attentional bias for food in overweight and obese people, Kaisari (2018) carried out a quasi-experiment.

The sample was made up of 43 overweight or obese participants and 49 healthy-weight participants. Participants were between 18 - 60 years old. The sample was a self-selected sample, recruited through posters, emails and mass mailings. To reduce demand characteristics, participants were told that it was a study of eating habits and memory. Any participants who had a history of an eating disorder were excluded from the study.

The two groups (overweight vs. not overweight) were exposed to two different conditions. They were either given a "food mindset" in which they were asked to memorize pictures of food items, or a "non-food mindset", where they were asked to memorize images that were not food related - such as a hammer. Then, they were asked to sit at a computer terminal and locate a circle as quickly as they could, while ignoring a distractor (a square). On some trials, the circle was accompanied by a food image; in other trials, the distractor was accompanied by the food image.

All participants found it harder to spot the circle when they were in a food mindset and it was the distractor, rather than the target circle, that was accompanied by an image of food. Crucially, however, the distracting effect of food and being in a food mindset was greater for the overweight or obese participants, suggesting they had a harder time disengaging from food. 

The participants also returned to the lab a year later for a weigh-in. The more that the participants’ task performance had been swayed by a food mindset, the greater their increase in BMI tended to be, indicating that the attentional processes uncovered in the lab have a real-life impact. The researchers argue that thinking about food increases the likelihood of overeating because a person is more responsive to the presence of food in the environment.

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