Intertemporal discounting as a risk factor for high BMI: Evidence from Australia, 2008

- Models are estimated exploring the relationship between intertemporal discounting and BMI.
- A monetary trade-off based indicator is shown to have a significant positive relationship with BMI.
- The estimated marginal effect of discounting on BMI is found to have a magnitude similar to education or income.
- An alternative health-based indicator of discounting is not found to have a significant relationship with BMI.

This paper explores the relationship between intertemporal discounting and body weight, using stated preference measures of intertemporal discounting, and the body mass index (BMI) to represent relative body weight. The empirical analysis uses Australian data obtained in 2008 through the South Australian Health Omnibus Survey. A quantile regression analysis is used to allow the marginal effects of the explanatory variables on BMI to vary across the conditional BMI distribution. It is shown that an indicator of intertemporal discounting elicited from a hypothetical monetary trade-off has a significant positive relationship with BMI. This relationship appears to be stronger in the upper quantiles, but there is insufficient statistical evidence for this difference. Evidence is presented that intertemporal discounting is a risk factor for increased BMI with a magnitude of effect comparable to more commonly recognized risk factors such as income and education. However there is no significant relationship found between BMI and an alternative indicator of intertemporal discounting elicited from trade-offs in health status.