Overweight people less likely to consider timing of next meal when choosing portion sizes

18 Jul 2017 --- People with obesity tend to ignore how long it will be until the next meal when choosing how much to eat, according to researchers at the University of Bristol. In a study designed see if people consider the time interval between two consecutive meals when deciding portion sizes, the researchers found that obese people tend to discount that information.

Obesity had previously been linked to differences in “delay discounting,” a tendency that had typically been studied by psychologists in tasks using money. Those with higher levels of delay discounting treat something as less significant based on how far in the future it will occur. It is a facet of impulsivity, encouraging decisions in the moment that disregard future rewards or consequences. In this study, for the first time, the researchers assessed how people with obesity discount information about future meal timings.

Participants in the study completed a series of computerized tasks, which included selecting lunch portion sizes after being told how long after lunch the next meal would be. The times ranged up to eight hours later. The researchers found that individuals with a high body mass index (BMI) were less influenced by information about the inter-meal interval when making portion size decisions. Additionally, participants completed a monetary delay discounting task. There was no interaction between the monetary delay discounting task and the inter-meal interval task, although both independently predicted BMI. This suggests that these factors work in parallel but tap into separate traits related to obesity.

“Meal timings and future planning are an important area of research in obesity,” says lead author Annie Zimmerman, a doctoral student at the University of Bristol. “These findings are exciting because they are the first to demonstrate that discounting operates in planning from one meal to the next and that people with obesity might not be factoring that into their choices.”

“Our results are consistent with the idea that overeating is promoted by feeling in the moment, disregarding future consequences of decisions. This novel finding might help to explain why being overweight is associated with irregular meal timings. Potentially there could be targeted interventions for obesity to promote future thinking in meal planning,” Zimmerman says.

“It is particularly interesting that monetary discounting was not related to sensitivity to future meal timings,” explains Zimmerman further. “The literature is beginning to differentiate between discounting of food and money – our findings are consistent with the idea that temporal discounting works differently for different reward types.”

“Our results highlight the need to distinguish between long-term monetary discounting and shorter-term discounting between meals. We need to develop a multifaceted model of discounting to fully understand the role of dietary discounting in eating behaviors and the links to obesity.”

The findings will be presented this week at the 2017 annual meeting of the Society for the Study of Ingestive Behavior (SSIB), the leading scientific society for research into all aspects of eating and drinking behavior.