Fats and oils play a prominent role in U.S. dietary patterns. Recent concerns over the negative health consequences associated with fats and oils have led many to suspect structural change in demand conditions. We consider short run (monthly) demand relationships for edible fats and oils. In that monthly quantities of fats and oils are likely to be relatively fixed, we utilize an inverse AIDS specification. Our analysis consists of two components. In the first, we utilize a smooth transition function to model a switching inverse almost ideal demand system (IAIDS) that assesses short-run demand conditions for edible fats and oils in the U.S. Our results suggest that short-run demand conditions for fats and oils experienced a rather rapid structural shift in the early 1990s. Although this shift generally made price flexibilities more elastic, differences in flexibilities across regimes are modest in most cases. Our results suggest that decreases in marginal valuations for most fats and oils in response to consumption increases are rather small. Scale flexibilities are relatively close to -1, suggesting near homothetic preferences for fats and oils. An important distinction occurs for lard and tallow, which exhibit a very elastic scale response. This suggests that scale increases in the consumption of edible fats and oils will significantly decrease consumers' marginal valuation of these animal fats. A second segment of our analysis considers dynamic extensions to the IAIDS model that recognize habit effects. Although nested hypothesis testing supports the dynamic specification over the static IAIDS model, price and scale flexibilities are quite similar to the static case.