Many believe that fast food promotion is a significant cause of the obesity epidemic in North America. Industry members argue that promotion only reallocates brand shares and does not increase overall demand. This study weighs into the debate by specifying and estimating a discrete/continuous model of fast food restaurant choice and food expenditure that explicitly accounts for both spatial and temporal determinants of demand. Estimates are obtained using a unique panel of Canadian fast food consumers. The results show that promotion primarily increases demand and has very little effect on restaurant market shares.