Foods comprising equal amounts of carbohydrate and fat are expected to be less satiating (yet more rewarding) than those comprising predominantly fat or carbohydrate.

Combining fat and carbohydrate (carb) increases food reward. Previously, we reasoned that a mechanism is reduced satiety - foods comprising a more equal ratio of carb and fat deliver less satiety per calorie. In an initial test of this theory, we completed two online data collections, one in the US (N= 148 participants, 36 foods) and one in the UK (N= 150 participants, 24 foods). In both, participants evaluated high-carb, high-fat, and 'combo' (equal fat/carb) foods. Consistent with our preregistered hypotheses, in both studies, combo foods were (1) rated more liked (taste pleasantness: UK Carb = Fat < Combo, p< .001, ƞp2= .33; US Carb = Fat < Combo, p< .001, ƞp2= .06), (2) rated more rewarding (desire to eat: UK Carb = Fat < Combo, p< .001, ƞp2= .30; US Carb = Fat < Combo, p< .001, ƞp2= .08) and (3) expected to be less satiating (comfortably full: UK Carb = Fat < Combo, p< .001, ƞp2= .29; US Carb = Fat < Combo, p< .001, ƞp2= .23). The results for other measures (hypothetical ideal portion (kcal) and maximum portion (kcal) and rated prospective sickliness) were also consistent with our pre-registered hypotheses (all p< .001). Together, these findings align with our theory that combo foods are more rewarding because they deliver less fullness. In turn, this pattern may reflect a form of nutritional intelligence, whereby food reward motivates the selection of foods that can maximise energy intake. However, research comprising causal studies is required to confirm or refute this claim.