This article describes the design, implementation and evaluation of digital learning material on the social--psychological Theory of Planned Behavior (TPB) and its use in nutrition behavior research. The design is based on guidelines derived from theories on instructional design. The major component of the design challenge is to implement three design guidelines: (1) the use of concrete examples from the field of nutritional behavior; (2) the use of Just in Time information presentation according to recent developments in theories about cognitive load; and (3) the promotion of active learning by stimulating the student to activities. These guidelines are designed to be used in the development of learning material that prepares students to apply the TPB in practical cases. The learning material and its use have been evaluated during two subsequent years in two different academic courses. Initial disappointing evaluation results could mainly be attributed to a discrepancy between design assumptions about the educational setting in which the learning material should have functioned and the actual setting in which the evaluation took place. In a second evaluation, in which the educational setting was adapted to the design assumptions, the learning material satisfied most of the design requirements.