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Abstract—Obesity is a major health concern caused by unhealthy eating behaviours. Digital weight loss interventions have adopted mobile technology primarily in order to support self-monitoring. However many available apps are not designed as part of dietetic practice; therefore a distinct gap in the research exists relating to technology that supports the patient-practitioner relationship. This paper presents myPace, which is a complete weight loss and management system that is deployed via a smartphone and a PC. It connects dietitians and patients between face-to-face consultations and extends the relationship through patients ’ regular progress updates and dietitians ’ tailored and timely advice, for sustained behaviour change. The prototype was developed from research into behavior change for weight loss, which furthermore was underpinned by theory and tenets of human support models, such as the supportive accountability framework. We report on early phase system design goals via a formative research process, which aimed to implement theoretical principles and match practical dietetic practice. To that end only the clinical end user’s perspective was sought through a coaching think-aloud protocol on the first iteration of the prototype and interviews with dietitians. Findings show that the system has many positive design features, but which require further development in order for the system to be fully acceptable within dietetic practice and motivate patient engagement. Index Terms — Behaviour change, healthcare practitioners, mobile health, supportive accountability, weight los