BACKGROUND/OBJECTIVES: The effect of Glycaemic Index (GI) and Load (GL) of breakfasts on satiety and aspects of cognitive function in children is inconclusive. We aimed to assess if isocaloric breakfasts differing in GL (by replacing high-GI carbohydrate foods with dairy protein foods) acutely alter cognitive function and satiety in 10- to 12-year-old children. SUBJECTS/METHODS: A total of 39 children, aged 11.6±0.7 years with body mass index 18.9±3.0 kg/m² (Mean±s.e.) participated in a randomised crossover trial of three isocaloric breakfasts (1.3 MJ): high GL (HGL: 7 g protein, 9 g fat, 50 g carbohydrate, GL 33); medium GL (MGL: 14 g protein, 9 g fat, 45 g carbohydrate, GL 24) and low GL (LGL: 18 g protein, 10 g fat, 38 g carbohydrate, GL 18). Blood glucose was recorded using a continuous glucose monitor. Subjective hunger and cognitive performance were measured before and hourly after consuming the test breakfast via a computer-delivered battery. Ad libitum intake at a buffet lunch meal was measured at 3 h at the end of testing. RESULTS: Incremental area under the glucose curve (iAUC) was significantly different with HGL>MGL>LGL (P<0.001). Glucose concentrations fell below baseline after 83±6 min for HGL, 63±5 min (MGL) and 67±5 min (LGL)(P=0.009). Breakfast GL did not significantly alter changes in cognitive function or self-reported satiety throughout testing. Energy intake at lunch was not significantly different between treatments (HGL 2943±168 kJ; MGL 2949±166 kJ; LGL 2993±191 kJ). CONCLUSIONS: Reducing breakfast GL by replacing carbohydrate with protein does not alter satiety or cognition over 3 h in 10- to 12-year-old children.