The microstructure of eating behavior reflects physical properties of food. Responses of lean and obese subjects to these physical properties are similar. For example, eating smaller bite-sized food units reduces initial ingestion rate and mean and local ingestion rate for the entire meal, but does not affect total intake in either lean or obese women. On the other hand, analysis of the microstructure of eating behavior also suggests that obese subjects are less hungry and are more motivated by food preferences than lean subjects. For example, in meals of bite-sized food units, initial ingestion rate is less affected by deprivation and more affected by food preference in obese than lean women. In buffet meals with a variety of foods, obese men eat dessert earlier in the meal, and eat more dessert and other energy dense foods than lean men. The research reviewed here suggests that treatments for obesity should not focus on modifying bite size and ingestion rate and other microstructural variables, which are largely determined by the physical properties of food. Instead, treatment should focus on food selection and the stimulatory effects of palatability on intake.