The mitigating influence of time preference on the relation between smoking and BMI scores.

Abstract

Prior studies have found a strong negative relation between smoking and body mass index (BMI). Smoking and unhealthy eating both imply a preference for utility in the present at the expense of future consumption. This analysis seeks to proxy this preference through a composite index of equally weighted intertemporal behaviors to isolate the impact of smoking upon BMI independent of time discounting. Ordinary least squares regression is used to analyze BMI score based on a number of key independent variables. A total of 2970 individuals who provided data for the United States Department of Agriculture's (USDA) Continuing Survey of Food Intakes by Individuals (CSFII) 1994-1996, as well as the Diet and Health Knowledge Survey (DHKS). Adding time preference to a multivariate model inflates the magnitude of the smoking effect, consistent with discounted utility theory. Results suggest that full effect of the non-intertemporal aspects of smoking (e.g., the substitution of cigarettes for food) on BMI scores may be underestimated in previous studies that fail to account for the mitigating influence of time preference.