We formulate an empirical learning model suitable for understanding individual behavioral responses in such environments. We estimate this model using data collected about the joint personal decisions of food selection, intake, and waste during a study in which users photographed their meal selections and plate waste over the course of a week with a cell phone. We found a substantial learning-by-doing effect in plate-waste reduction: Those who document greater plate waste in their captured photographs waste less on subsequent days. Further, we identified that participants reduced plate waste by learning to eat more rather than by learning to reduce the amount of food selected.