  Obesity is a serious disease that can affect both physical and psychological
well-being. Due to weight stigmatization, many affected individuals suffer from
body image disturbances whereby they perceive their body in a distorted way,
evaluate it negatively, or neglect it. Beyond established interventions such as
mirror exposure, recent advancements aim to complement body image treatments by
the embodiment of visually altered virtual bodies in virtual reality (VR). We
present a high-fidelity prototype of an advanced VR system that allows users to
embody a rapidly generated personalized, photorealistic avatar and to
realistically modulate its body weight in real-time within a carefully designed
virtual environment. In a formative multi-method approach, a total of 12
participants rated the general user experience (UX) of our system during body
scan and VR experience using semi-structured qualitative interviews and
multiple quantitative UX measures. By using body weight modification tasks, we
further compared three different interaction methods for real-time body weight
modification and measured our system's impact on the body image relevant
measures body awareness and body weight perception. From the feedback received,
demonstrating an already solid UX of our overall system and providing
constructive input for further improvement, we derived a set of design
guidelines to guide future development and evaluation processes of systems
supporting body image interventions.
