A qualitative study to examine meaningful change in physical function associated with weight-loss

Purpose This study explored perceptions of meaningful weight-loss and the level of change on two patient-reported outcome (PRO) measures, the 36-item Short Form Health Survey (R) [SF-36v2 (R)] and Impact of Weight on Quality of Life Lite-Clinical Trials (c) [IWQOL-Lite-CT (c)], that individuals living with overweight or obesity consider to be meaningful and indicative of treatment success. Methods Thirty-three qualitative interviews were conducted in the US with adults living with overweight or obesity. Concept elicitation explored perceptions of minimally important/meaningful weight-loss using open-ended questions. Cognitive debriefing was used to understand thresholds for meaningful change on both measures. Results Most participants (n = 23/33) expected a 5% total body weight-loss to yield some benefit in physical functioning, while all participants expected a 10% weight-loss to provide a meaningful and noticeable improvement in their physical functioning. Participants indicated that an item-level 1-point score change on each measure would represent a noticeable improvement in physical functioning and indicate treatment success. Conclusions Participants expected moderate weight-losses to be noticeable, with >= 10% weight-loss yielding the most consistent results. The findings suggested that both measures provide strong opportunity to demonstrate treatment benefit in relation to physical functioning as a small change on the response scale would represent a noticeable improvement in participants' daily lives.