Obese and impulsive? The two may be linked, a Malta medical study finds

Weight can be used as an indicator for one’s propensity to taking evidence-based decisions, according to the results of a study by Maltese doctors.

The study, published in the Malta Medical School Gazette, compared impulsivity in subjects with a body mass index (BMI) over 30 to that of healthy volunteers.

It found that obese subjects accumulated less evidence prior to decision-making, along with a trend towards “enhanced delay discounting” – the likelihood that a person opts for an immediate reward over a larger reward further in the future.

The study’s focus was an assessment of decisional impulsivity in the Maltese population.

In introducing the work, the authors note that elevated levels of impulsivity have been clearly shown in various psychiatric conditions, especially those of addiction. They say that while evidence does suggest some overlap between addictive use of food and the use of drugs, no clear evidence has to date been made available with regards to obesity.  

In their investigation, the researchers selected 30 obese individuals having a BMI over 30, as well as 30 healthy volunteers with a BMI below 26. All selected individuals were aged between 18 and 75.

Subjects in the study were asked to take three different tests. The first test, which assessed impulsive choice, involved subjects being presented with 27 questions in which they are asked to choose between a small immediate reward and a larger reward at a later point in time.

A second test gauged whether subjects were more likely to consider and deliberate over alternative solutions to problems, or whether they were more likely to respond spontaneously and without much deliberation. In this test, subjects were shown two jars with opposite ratios of red and blue beads. 80% of the beads on one jar were blue with the remaining 20% being red. The composition of the second jar was 80% red, 20% blue.

Subjects were then presented individual beads from one of the two jars and were asked to infer which jar the beads had come from.

The final task tested subjects’ waiting impulsivity or their tendency to prematurely respond to a computer-generated test.

Of the 30 obese subjects, 14 fulfilled the criteria for binge eating disorder. Compared to healthy volunteers, obese subjects reported significantly higher scores on depression, anxiety, binge eating and impulsivity.

The study found that there were no differences in the level of premature responding between the two groups.

As regards the subjects’ tendency to accept an immediate reward over a larger reward in the future, the results showed that obese subjects were more likely to take an immediate reward, however the differences were not great enough to eliminate the possibility that they were due to chance.     

A clear statistical difference was, however, observed in the beads test, with obese subjects requiring fewer beads before feeling comfortable enough to make a decision.

The results, argue the researchers, suggest the need to develop effective therapeutic interventions aimed at training individuals in the consideration of the future consequences of their decisions.