To compare the importance of cognitive factors relative to physiological factors for estimating food consumption and satiety, we served 64 participants lunch in a dark restaurant where they ate a regular two-course meal in complete darkness. Half the participants unknowingly received considerably larger portion sizes which subsequently led to higher food intake. Despite this difference, participants appetite for dessert and their subjective hunger after the meal was largely unaffected by the amount of food they had consumed in the dark. In comparison, 32 participants in a control group who ate the same meal in the light consumed comparatively less food from the large portion and still compensated for the larger portion size by eating less dessert afterwards. Together, these results indicate that internal physiological cues do not provide accurate feedback and that visual cues are the main source of information for estimating food intake and satiety.