Obesity and temporal discounting
Ciosa Garrahan and Juliet Hodgeson 23 May, 2014 at 11:05
A recent study published in Appetite has shown a robust relationship between body mass index and choosing immediate over delayed rewards. Overweight and obese participants were more likely to choose £100 today than £110 in a week than normal and underweight participants were, although these differences decreased when the delayed rewards increased.
The authors concluded that the heavier participants had higher temporal discounting rates, which means the delay of the reward had a greater effect on reducing its perceived value than it did for the lighter participants. This suggests that finding ways of increasing cognitive control could be key to obesity interventions, assuming a preference for instant money rewards also applies to their diet and lifestyle choices.
However, it must be noted that this finding is only a correlation and does not prove causality. The likelihood to choose a delayed reward over an immediate one is related to activity in the prefrontal cortex and the anterior cingulate cortex.
Studies have shown that a healthy diet and physical exercise increase prefrontal function, but both behaviours are negatively correlated with obesity. Therefore, preferences for immediate rewards may be a symptom of lifestyle factors associated with obesity, rather than a cause of obesity itself. In addition, previous studies have found that discount rates in one domain do not always consistently translate to others, such as money, food and environmental concern.