ASSESSING THE INFLUENCE OF DELAY DISCOUNTING OF FUTURE HEALTH ON DIET AND PHYSICAL ACTIVITY BEHAVIORS: DOES IT DIFFER BY BODY MASS INDEX CATEGORY?

Purpose: Delay discounting is a measure of how individuals value the future, with higher rates of discounting indicating lower value of future rewards.  Previous research has demonstrated a negative association between degree of discounting and certain preventive health behaviors, but the influence of weight status on this relation has not been studied.  The objective of this study was to determine whether degree of delay discounting influences healthful diet and physical activity (PA), and how this differs in overweight/obese individuals compared to underweight/healthy weight individuals.

Method: Computer-administered surveys were conducted in adults (n=172). Items included diet and PA behaviors, height, weight and demographic variables. Body Mass Index was calculated using self-reported height and weight and used to categorize participants as underweight/healthy weight (<25) or overweight/obese (>=25). Degree of delay discounting for both health and monetary rewards was assessed separately using a binary choice, decreasing adjustment algorithm, and was measured using normalized area under the delay discounting curve (AUC).

Result: More than half (53.6%) of participants were categorized as either overweight or obese, based on self-reported height and weight. AUC was not significantly correlated with preventive behaviors for either health or monetary rewards in the overall sample.  Mean square root-transformed AUC for monetary rewards was significantly lower (indicating a higher discount rate) in overweight/obese individuals (0.516 ± 0.219) compared to underweight/healthy weight individuals (0.590 ± 0.236) [t(166) = 2.11, p=.037]. Fewer overweight/obese participants met the guidelines for weekly PA (62%) compared to underweight/healthy weight participants (84%) [X²=9.96, p=.002]. Diet score was significantly lower for participants identified as overweight/obese (25.8 ± 7.04) compared to those categorized as underweight/healthy weight (29.9 ± 6.27) [t(166) = 3.95, p<.001].  AUC for monetary rewards was significantly correlated with diet score in underweight/healthy weight individuals (r=.255, p=.024), but not in overweight/obese individuals.

Conclusion: No association between degree of discounting and behavior was detected in the overall sample. However, when the sample was divided according to weight status, better diet quality was associated with greater value of the future in underweight/healthy weight individuals, but not in overweight/obese individuals. This may indicate a more complex association between self-controlled choice and behavior in overweight/obese individuals. Further research using larger sample sizes is needed to untangle these complex associations.