Purpose: A health learning program relying on the scientific method was designed to promote reducing the intake of foods high in sugar, sodium and saturated fat in a group of school-aged children. Design/methodology/approach: The scientific method was a core approach for creating intervention activities. We conducted mixed-methods research consisting of a quasi-experimental study and supplemented with a qualitative study. Findings: After the intervention, mean scores of knowledge (F = 16.052, p < 0.05) and intrinsic motivation of the intervention group (IG) were significantly increased (t = 4.277, p < 0.05). Although basic science process skills before and after intervention were not significantly different, it found positive correlations with intrinsic motivation, extrinsic motivation and dietary behavior. Research limitations/implications: The selected sample size is relatively small. The intervention program should be repeated with larger and more diverse students to ensure the effectiveness of this program. Practical implications: This intervention program relying on the scientific method evokes the knowledge of grade 5-6 students about good diet and nutrition, emphasizing reducing the intake of foods high in sugar, sodium and saturated fat. Teachers should also observe and encourage students to steadily drive healthy food consumption behaviors according to the theoretical behavior change stage at least during their time at school. Originality/value: The developed program could be a feasible option for teachers to integrate into the lessons in the classroom. This program also motivates students' healthy food consumption.