The effects of food unit size (FU) and energy density (ED) on food consumption were explored in 20 adults using a within subjects 2 x 2 design study. The four food treatment combinations were provided in the laboratory in random order on four non-consecutive days. The foods differed in FU (small food unit (SFU) or customary food unit (CFU)) and energy density, by manipulating fat content (low (LED) or high (HED)). Appetitive responses and total grams and kilocalories consumed were monitored. Hunger, fullness, desire to eat and prospective consumption ratings were not significantly different between treatments. Gram weight of food consumed was constant across all treatments. Energy intake of HED foods was greater than LED foods independent of food unit size for breakfast (F(1,17) = 11.77, p < 0.001), lunch (F(1,17) = 4.70, p < 0.05) and the 24 h period (F(1,17) = 8.99, p < 0.001) but only tended to be increased at dinner. In summary, appetitive sensations were not markedly altered by food unit size or energy density. The daily gram weight of food consumed and appetitive ratings were relatively consistent across treatments resulting in higher energy intake with HED foods.