Unhealthy diets, obesity and time discounting: a systematic literature review and network analysis

There is an increasing policy commitment to address the avoidable burdens ofunhealthy diet, overweight and obesity. However, to design effective policies, it isimportant to understand why people make unhealthy dietary choices. Researchfrom behavioural economics suggests a critical role for time discounting, whichdescribes how people’s value of a reward, such as better health, decreases with delayto its receipt. We systematically reviewed the literature on the relationship of timediscounting with unhealthy diets, overweight and obesity in Web of Science andPubMed. We identified 41 studies that met our inclusion criteria as they examinedthe association between time discount rates and (i) unhealthy food consumption;(ii) overweight and (iii) response to dietary and weight loss interventions. Nineteenout of 25 cross-sectional studies found time discount rates positively associated withoverweight, obesity and unhealthy diets. Experimental studies indicated that lowertime discounting was associated with greater weight loss. Findings varied by howtime discount rates were measured; stronger results were observed for food thanmonetary-based measurements. Network co-citation analysis revealed a concentra-tion of research in nutrition journals. Overall, there is moderate evidence that hightime discounting is a significant risk factor for unhealthy diets, overweight and obe-sity and may serve as an important target for intervention.