The rising prevalence of non-communicable diseases calls for more sophisticated approaches to support individuals in engaging in healthy lifestyle behaviors, particularly in terms of their dietary intake. Building on recent advances in information technology, user assistance systems hold the potential of combining active and passive data collection methods to monitor dietary intake and, subsequently, to support individuals in making better decisions about their diet. In this paper, we review the state-of-the-art in active and passive dietary monitoring along with the issues being faced. Building on this groundwork, we propose a research framework for user assistance systems that combine active and passive methods with three distinct levels of assistance. Finally, we outline a proof-of-concept study using video obtained from a 360-degree camera to automatically detect eating behavior from video data as a source of passive dietary monitoring for decision support.